Now, nine homebuyers have said that Bovis representatives offered them rewards if they agreed to fill in the HBF customer satisfaction form, the results of which are used to inform the annual ratings.

Five customers say the incentives were offered in return for positive feedback, something Bovis adamantly denies.

The homebuyers spoken to by The Independent bought their properties at different Bovis developments between 2016 and 2018.

Charlotte and Michael Kenton, who purchased their home in Bedfordshire in June 2016, claimed their site manager offered them high street vouchers in return for positive feedback.

“He said it was directly linked to his bonus so if we were happy with the sales process we should give him 5 stars and he could ‘make it worth our while,” they said.

Another couple claimed a Bovis employee offered free turf and John Lewis vouchers in December 2017 if they gave good feedback on the HBF survey or if they let the Bovis sales representatives fill in the form themselves.

In a further example, a homebuyer who bought her property in Oxfordshire in January 2017, said she was offered vouchers if she gave a positive response to the question of whether she would recommend Bovis to a friend.

She said: “We filled out the [HBF/NHBC] survey, gave 1 star at most, but we were told we would be given £500 worth of vouchers if we recommended Bovis to a friend.”

Another homebuyer, who wished to remain anonymous, said her site manager told her in February 2017 he would extend her patio for her if she gave him a good review.

She told The Independent: “I was advised by the site manager that the feedback form was very important and if you scratch my back, I’ll scratch yours… he intimated that he would contribute towards turning a side garden into an extra parking spot if we looked after each other…”

In another instance, in February this year, a Bovis site manager sent a customer an email – seen by The Independent – confirming that the company would pay a month’s worth of household bills but appeared to require her to complete the HBF survey before sending copies of her bills.

The buyer was sent a cheque for more than £1,000 after she completed the survey.

The Independent understands that Bovis had advised the customer that the payment was compensation for inconvenience after the homebuyer’s kitchen was damaged (and not related to the survey).

Four other homebuyers, who have spoken to The Independent on condition of anonymity, were allegedly offered bottles of champagne, chocolates or contributions towards remedial work if they agreed to complete the survey.

Bovis stated that up until May 2016, it ran a programme offering customers incentives to complete feedback forms – irrespective of whether the response was positive or negative – but said the practice had been stopped.

Five of the nine homebuyers spoken to by The Independent claim they were offered incentives after Bovis told its representatives to change the policy.

HBF’s national survey of housebuilders was launched in 2005 in response to recommendations in the Barker Review of Housing in 2004 and results determine a house builder’s annual rating. Since 2013, ratings are based on just the one question: ‘Would you recommend your builder to a friend?’

In a statement, Bovis said it had made significant changes to its build quality and customer service, which had transformed the company. It added that it had a strict policy with regards to the HBF customer survey.

A spokesman said: “Currently more than 87 per cent of our customers across the country would recommend us to friends and family, representing a 30 percentage point improvement on where we were at the same time last year.

“There are strict rules around the management of the HBF customer survey and we are absolutely committed to adhering to those.

“In the current survey year, which started on 1 October 2017, we have so far received more than 740 surveys, and around 87 per cent of those returned would recommend us to family or friends.

“If there is any evidence that any one of those hundreds of positive responses – or any from previous years – were not returned according to the rules, then we would wish to see that evidence and we would investigate it thoroughly.”

In relation to the case in which £1,000 of a homebuyer’s bills had been paid, Bovis said it was investigating the claim that payment had been conditional on the customer completing her feedback form.

A spokesman said: “On this point, we are currently investigating one claim made by a customer to The Independent, where it appears that our processes and procedures have not been followed and the colleague involved has been removed from site while we make further enquiries.”

When new CEO Greg Fitzgerald took charge of Bovis – after the resignation of David Ritchie in January 2017 – he promised to ensure that the house builder was no longer “handing over crap or incomplete houses to customers”.

Mr Fitzgerald, who made the statement after Bovis was found to have been paying homebuyers as much as £3,000 to move into unfinished homes in a failed attempt to reach an ambitious target of completing 4,131 houses by the end of the financial year, served six years as a company director for the National House Builders Council, the UK’s main home construction warranty provider, prior to his appointment.

However, The Independent has been told by several homebuyers that problems with quality remain.

Allison Briggs, 49, said that her hi-spec washing machine was broken on the day she moved into her property on a development in April 2017.

When Bovis later replaced it, she claimed the whole house vibrated when was the washing machine was on.

She told The Independent: “I am living in a Bovis nightmare. I wish I could walk away.”

Another, who bought their property in January 2017, said they had experienced problems immediately. But when they approached Bovis, the house builder allegedly told them the house being situated on a corner caused the issues.

They told The Independent: “We raised the issue again with Bovis and yet again we were told every excuse possible.”

In a statement, Bovis said: “We are committed to continuing to drive through these improvements in our business and to deal with any customer issues by our home warranty.

In those rare instances where items might be disputed, then we welcome the involvement of external agencies, such as the NHBC, to objectively assess the issues, and we are committed to meeting all of our obligations in these instances.”

“We apologise to any customer who did not move into the home they deserved in the past, but we are concerned that using isolated historic case studies as a reflection of our current performance misrepresents the business and will have a negative impact for those thousands of satisfied Bovis Homes customers who are not being contacted by the media for their experiences of buying a new-build home.”

Buyers across the UK claim the house builder sells properties that are “not fit for purpose”, with some residents reporting issues relating to insulation, flooding, structural issues and rendering.

A Facebook group called Bovis Homes Victim Group has grown to more than 3,000 members and common complaints among them are a lack of sound insulation, incorrect appliances, dented doors, flooding and thermal issues.

A number of disgruntled homeowners have reached settlements with Bovis, the terms of which are sometimes protected by non-disclosure agreements.

Bovis said: “We want open and honest feedback – positive and negative – from all of our customers so that we can build on the major improvements we have driven through the business and further enhance the experience of buying a Bovis Home.”

Dave Howard, a founder of the group, which operates the domain http://www.bovishomesvictimsgroup.co.uk and the owner of a £400,000 home in Oxfordshire, said he continues to work closely with the firm.

“We continue to attempt to work constructively with Bovis Homes as members of its Homebuyers Panel but have yet to detect any noticeable improvement in either build quality or customer service.