A report by the Public Accounts Committee (PAC) warned that “shoddy treatment” experienced by staff who have come forward with allegations of wrongdoing may deter other employees from speaking out.

“Whistleblowers are on the frontline of defense against wrongdoing and bad practice,” PAC chair Meg Hillier said.

“They have a vital role to play in the day-to-day accountability of public spending and public service. This should be recognized by and enshrined in the culture of every government department. Where it isn’t, senior officials in those departments should be held properly to account.”

In response to the PAC report, the Cabinet Office has started collecting data on whistleblowing cases across departments.

The first batch of data showed more than half of the 68 reported cases between April and September of 2015 were made anonymously.

“At this stage, a common theme emerging is that the majority of complaints were made anonymously,” the Cabinet Office said.

Fourteen of the government’s 32 departments, including the Department for Work and Pensions (DWP) and the Foreign and Commonwealth Office (FCO), reported cases of whistleblowing over the period.

The Cabinet Office said the findings indicate most officials do not “have the confidence in their departments to deal with their case appropriately.”

In light of the findings, the Cabinet Office urged departments to “provide assurance to employees to enable them to raise their concerns openly.”

However, the office acknowledged the project was a work in progress and that they would need to continue to collect further data sets.

“This is the first time whistleblowing data has been collated centrally and there are wide variations in the data being reported,” the Cabinet Office said.

“A well-evidenced assessment of systemic issues or concerns will take time to emerge, and will be possible once multiple data sets are available.”

Angus MacNeil, a senior figure in the Scottish Nationalist Party, repeatedly claimed expenses for a room at the four-star Park Plaza near the House of Commons. His lover – 36-year-old Serena Cowdy – claims that she frequently spent the night there with him.

She is now having an affair with the 45-year-old’s fellow SNP MP Stewart Hosie.

” … Since David Cameron became prime minister, the amount that MPs claim each year [for expenses] has risen by 43%. Total business costs and expenses rose from £79m in 2010/11, to £113m in 2014/15. Parliamentarians are claiming more and more on things such as air travel and rent.

Flight expenses have gone up 50%, now standing at more than £1m a year. Expenses for renting second homes have risen from £6.2m before, to £9.3m in 2014/15. As for the great transparency push? In fact, the data that Ipsa now publishes with great pride online would not, in itself, be enough to expose the worst abuses of the 2009 scandal. Many of those – the trick of “home flipping”, for instance – were only uncovered because the Telegraph got hold of the original, uncensored files.

Crucial details – such as the full names of every company that politicians have paid money to – are not included in Ipsa’s prized new database. There is one way around this: the original documents can sometimes be accessed by making a request under the Freedom of Information Act and waiting four weeks for Ipsa to respond. But, even then, the documents often arrive in your inbox redacted with black ink.

Although some MPs are happy with the new system, a great many resent the restrictions over what they can claim. “They get very touchy about things called taxis,” a Tory MP tells me. “MPs aren’t allowed taxis because it’s emotive. Ipsa aren’t interested in what’s fair – they’re only interested in the rules. MPs call it “I’m Paid Sod All”.’

An anonymous survey of MPs that Ipsa conducted in 2014 revealed some remarkable attitudes from a Parliament that is meant to have moved on from the expenses scandal. One MP called for a return to “paper-based claims”, saying: “I work 60/70 hours a week and resent being used as your unpaid data-entry clerk.” Another called for transparency to be curbed so that she could travel first class without the press finding out. “It’s very difficult to work in standard class,” she complained. “But if you go first … Ipsa still publishes it as first-class travel and the papers love ‘greedy MP’ stories … It really annoys me.”

With many other expenses curbed by Ipsa’s new rules, hotels are one of the few things remaining that MPs can really go to town on. In one year alone, they claimed more than £700,000. The vast majority of this bill was for places in London, rather than overseas travel. I visit one glitzy hotel, not far from the Houses of Parliament, where dozens of MPs choose to spend the night. Their bills are claimed on expenses and charged to the taxpayer. This is by no means the most luxurious hotel in the world, but guests get free access to a swimming pool, sauna, steam room and gym. There’s also a “paradise” spa, where you can get full beauty treatments.

One MP in particular has maxed his bills at this hotel: the Conservatives’ Andrew Bridgen. When his marriage broke down a few years ago, Bridgen ditched his Westminster flat and adopted the hotel as his new pad. One year, he stayed here for 45% of the time – a total of 165 nights. Inevitably, Bridgen racked up a huge bill, amounting to nearly £25,000. Then he claimed it back on expenses. This is the same Andrew Bridgen who proudly told me: “I used to earn £1m a year.” His bills have gone down somewhat lately, but he still frequents the place.

When I ask Bridgen if it is acceptable for MPs to claim £150 a night for hotels, I hit a nerve. “I mean, what do you want?” he snaps. “We could get some cardboard boxes and kip out on the bridge at Waterloo station. That would be handy, although we might look a bit of a mess when we arrive to work the next morning… Where do you want us to go?”

“Is it a nice hotel?” he laughs. “No, it’s bloody awful. I’d rather be at home.”

Bridgen sees nothing distasteful about the fact that he – and many of his colleagues – charge taxpayers for his second life in a hotel. He reckons it’s “cheaper than having a flat”, and adds: “I stay at the [hotel] because it’s a quick walk. When we finish late at night – [I can] just walk home.”

A close look at Ipsa’s files reveals that MPs claimed more than £156,000 on hotels in the first two months after the 2015 general election. Among them were two Tory MPs – Mike Wood and Andrew Turner – who enjoyed nights at London hotels owned by the Ritz-Carlton chain, together claiming more than £500 on expenses.

The Ritz-Carlton group owns three places in London, all of which describe themselves as “luxury” hotels: the Bulgari, the London Edition hotel and the Ritz hotel itself. In another case, the disgraced former Labour minister Eric Joyce racked up a £426 bill for two nights in a hotel in Glasgow, before he left Parliament in 2015. It was just 40 minutes’ drive from his own constituency.

The Hotel du Vin describes itself as a “luxury boutique hotel with that little bit more”, adding: ‘The most famous of Glasgow’s hotels has an enviable reputation for service and style, with 49 stunning bedrooms and suites, bistro, bar, cigar shack and whisky room.” Afterwards, Joyce kept hold of his receipt and tried to claim back part of it on expenses. He was rebuffed by Ipsa, who told him it did not fall under the scheme.

Most MPs don’t live their lives out of hotels. But that doesn’t mean their lifestyles aren’t still fuelled by taxpayer cash. Rents in London are notoriously expensive. In summer 2015, the average monthly rent in the capital hit £1,500. But MPs need to live somewhere convenient for work, and we shouldn’t expect it to come cheap. Still, if they already have a main home in the constituency, maybe a one-bedroom flat would be sufficient for weekdays. But no. Dozens treat the average as the bare minimum.

Using the Freedom of Information Act, I unearthed copies of some of the housing contracts that politicians have signed. At the top of the pile of big spenders are MPs such as Simon Danczuk, who has claimed £2,142 per month for rent. In a letter to Ipsa, he said this was “within my budget”. But it wasn’t him who was paying – it was the taxpayer.

Another MP, Ian Paisley Jr, used to claim £2,592 a month on rent, which you might think was enough. But in September 2015, he signed a new contract, worth £2,925 a month. Government minister George Freeman has been charging taxpayers £2,817 per month for his room in Bloomsbury. Meanwhile, his colleague in the Home Office, Karen Bradley, moved into a shared property in Little Venice, west London. She claimed the £2,167 monthly rent on expenses. One new Labour MP, Marie Rimmer, managed to fix up her accommodation before she was even elected. Documents suggest she was given the keys to her Westminster flat a month before the 2015 general election. Her set-up meant she would not miss a day of expenses. Indeed, one of Rimmer’s rent claims is dated for the very next day after the election.

If MPs’ rent claims aren’t excessive enough, it turns out that some of them are cashing in twice. Many own properties in London, but rent another place out on expenses, regardless. This allows them to operate a double-rent system: flat one is where the MP lives, with rent covered by expenses; flat two is the place they actually own, where they act as a landlord and rent it out to other people.

Research by Channel 4 News in 2015 found that at least 46 MPs had this kind of system in place – a move that one Labour backbencher described to me as “a new fiddle”. Channel 4 reported: “Our investigation found many of the MPs bought their London properties with the help of the taxpayer, when the previous expenses system allowed them to claim back mortgage payments. But when those claims were banned, following the expenses scandal, they switched to letting out their properties, in some cases for up to £3,000 a month. They then started claiming expenses for rent and hotels in the capital.”

It was only later, when the Press Association made enquiries under an FOI request, that it was revealed the baroness had charged taxpayers £230 for her night at the opera. A chauffeur-driven Mercedes took D’Souza to the event in Covent Garden, just one mile from Parliament. The driver then sat outside for four hours waiting for the concert to finish, before taxiing her back to Parliament again. If she had caught the Tube, it would have cost £4.60.

The night at the opera was just one of a catalogue of D’Souza’s controversial expenses receipts that the Press Association had got hold of. Others included a £627 chauffeur bill to drive to the enthronement of Archbishop Justin Welby in 2013. She attended with John Bercow, the speaker of the House of Commons, but the pair took separate cars for the same trip. Bercow claimed an additional £525 for the journey.

Perhaps the most politically embarrassing small expense that politicians have claimed repeatedly is for poppies and wreaths. During the expenses scandal, Boris Johnson and ex-shadow chancellor Ed Balls were both exposed for claiming money to cover Remembrance Sunday wreaths. More recently, in 2015, Labour MP Sarah Champion was also caught claiming £17 for a poppy wreath.

And when they are talking anonymously, political insiders will happily defend such expenses claims. One senior special adviser says: “I spent a bloody fortune over the last couple of years on poppies … You’ll get a kicking if you’re not wearing a poppy – like in the press, or wherever. So you always have to make sure you’re wearing one. But then, you change your suit the next day and you forget. You’re getting on the tube in and you think: ‘Oh for fuck’s sake, I’ve left the poppy on the other suit.’ So you’ve got to go and buy another one. It’s not very much money, but over the course of bloody November, or whatever … it’s going to add up.”

Ridiculous claims are even filed by top government figures. Among the many receipts I uncovered was one from the health secretary, Jeremy Hunt. In 2014, he used his expenses to buy expensive designer glasses for his staff. Official work guidelines say that employers should contribute to the cost of spectacles, if staff need them to use a computer. But the health secretary filed claims on behalf of his staff covering the entire cost. Documents show that one of his staff visited Chandlers Opticians in Surrey and bought a £275 pair of glasses, which Hunt then billed to taxpayers. A second opticians’ bill for another staff member was also filed on Hunt’s expenses. This time, it covered a £25 eye test and a £180 pair of glasses.

It seems Hunt was fully aware that the expenses claim was being made. He told me: “In advance of submitting the claim, my office checked it specifically with Ipsa to ensure that everything was being done in the proper way – and we would contest any allegation to the contrary.”

It may have been within the rules, but the health secretary ducked my question: was it appropriate? Of course, Hunt was only following in the footsteps of his predecessor at the Department for Health, Andrew Lansley, who claimed £229 for prescription glasses and eye-test costs for an adviser in 2013.

Expenses claims such as this leave some insiders less than impressed. “When you employ staff in a business, you don’t pay for their f…ing glasses,” one ex-MP says. ‘Literally unbelievable!’

So what is the best way to police an expenses system? The dilemma may be familiar to any business manager: set up a system that relies on trust and some people will be untrustworthy (most of them, in this case); but go the other way and impose strict rules and they will play those rules. Tell them they can claim up to a maximum, and that maximum soon becomes a target to be aimed at.