The threat is a blow to the government’s £600bn infrastructure programme, which is already struggling to attract bidders. Last week the National Audit Office said there was little evidence that private finance initiative deals offered value for money for taxpayers.

Carillion plunged into insolvency last week with just £29m cash in the bank. Its threadbare finances were undone by failings on a string of PFI contracts, which left it unable to access hundreds of millions of pounds.

Balfour Beatty, Britain’s biggest construction company, has been moving away from fixed-price PFI contracts, which leave the winning bidders vulnerable to big losses if the projects encounter unexpected problems. The £2bn company is emerging from a disastrous spell of contract problems, which led to seven profit warnings.

Galliford Try — Carillion and Balfour Beatty’s partner on the Aberdeen bypass PFI contract — is also refusing to consider new fixed-price deals.

Rupert Soames, chief executive of the outsourcing giant Serco, said contractors would refuse to bid if too much risk were piled on them.

“Government would say, ‘You signed the bloody contract.’ But it’s not in anyone’s interest if you consistently get suppliers making huge losses. That’s no way to encourage a vibrant market. Both sides need to learn lessons from this,” said Soames, whose company’s government contracts include running prisons.

Balfour Beatty said in a report: “We need to move away from the position where fixed-price contracts, risk transfer, lowest-cost tendering and adversarial relationships are the norm.”

Carillion’s crisis was exposed in July when it admitted that contracts to build the bypass, Birmingham’s Midland Metropolitan Hospital and the Royal Liverpool Hospital were to blame for a large chunk of an £845m writedown. All three deals were public-private contracts, which left Carillion to foot the bill for cost overruns. There were unexpected problems in Aberdeen and Liverpool.

Despite this, the government wants contractors to bear all the risk on two huge PFI projects: a £1.6bn tunnel to bypass Stonehenge in Wiltshire and the £1bn Silvertown tunnel in east London.

Stephen Rawlinson of the analyst Applied Value, said: “The government has become more and more of a bully and transferred risk that the private sector cannot cope with.”

Jeremy Hunt and NHS England’s latest big idea is Accountable Care Organisations (ACOs). These bodies would be allowed to make most decisions about how to allocate resources and design care for people in certain areas.

At the moment, that’s done by public bodies whose governance is regulated by statute, set up by parliament after wide consultation and sometimes fierce debate. ACOs, by contrast, can be private and for-profit bodies. They are not mentioned in any current legislation and would have no statutory functions. They are not subject to the statutory duties imposed on other parts of the NHS.

Although NHS England plan to get several ACOs up and running this year, no detailed policy proposals have been presented to parliament or the public. Indeed, details are so sparse that the House of Commons library briefing is forced to use definitions provided by the King’s Fund, a health think tank.

Hunt is planning to lay a raft of secondary legislation – which doesn’t require a full parliamentary vote – in February, so that the first ones can be up and running by April 1st.

The ACOs are going to be given long-term commercial contracts of between ten and 15 years. We know these are difficult to get right and expensive to get out of. Think of Virgin and the East Coast Main Line or the private finance initiative, which has left the NHS paying hundreds of millions to offshore finance companies for hospitals that cannot now be afforded. Warnings about risks of PFI were once brushed aside as alarmist, often by the same people who now dismiss criticism of ACOs in similar terms.

I’m working with four colleagues to challenge these proposals through judicial review. Our case is not concerned with whether ACOs are a good or bad idea. That’s for parliament and the public to decide, not the courts. Our case is that such a radical and significant change cannot lawfully be introduced and implemented without public consultation, parliamentary scrutiny and primary legislation. The case was filed on December 11th and clearly struck a chord with the public. They’ve provided £176,000 through crowd funding in over 6,000 donations.

We are also deeply concerned that by using contracts instead of statute to allow ACOs to operate, the government is exposing the NHS to major risks.

We’re concerned that ACOs will be governed only by company and contract law, yet can be given “full responsibility” for NHS and adult social services. Because they span free health care and means-tested social care, ACOs will be able to decide on the boundary of what care is free and what has to be paid for. They can include private companies – including private insurance and property companies – which will make money from charging. Their accountability is unclear, in spite of their name, yet they will be given long-term contracts and be allowed to make “most decisions” about how to allocate NHS resources and design care for the local population. They will have control over the allocation of huge amounts of taxpayers’ money, yet their accountability for spending it and their obligations to the public would be under commercial contracts instead of statutes. The parallel with railway franchises seems inescapable. And by establishing them this way, it’ll be harder to exclude ACOs from free trade deals.

Lots of serious people are genuinely worried and object to their fears being brushed aside. If ACOs are not opening the door to greater privatisation of the NHS, why is their detailed documentation so explicit that they can indeed be private bodies?

We are not zealots opposed to change. We’re simply people who care about the founding principles of the NHS, have taken the trouble to read the small print and have the experience and knowledge to understand its implications.