Profits at Britain’s three biggest builders have quadrupled since 2012 to £2.2 billion, yet they regularly cite financial constraints when cutting affordable homes in developments. Builders miss targets for affordable homes in the countryside by 18 houses a day, research by the Campaign to Protect Rural England (CPRE) shows.

Profits at Barratt Developments, Britain’s biggest developer, increased almost sevenfold from £100 million in 2012 to £682 million last year. Meanwhile, the number of affordable homes fell from 23 per cent of the total built in 2012 to 17 per cent last year.

Developers use “viability studies” under planning laws to pressure local authorities into cutting the requirement for affordable homes. The reports are kept confidential, on commercial grounds, but documents seen by The Times show that officials from the Department for Communities and Local Government (DCLG) ruled that 20 per cent profit was a “reasonable” margin for a developer. They backed a builder’s attempt to cut the number of affordable homes at a development in Gloucestershire to safeguard that return.

Sajid Javid, the communities secretary, has said that failing to fix Britain’s “broken housing market . . . would be nothing less than an act of intergenerational betrayal”.

Research by the CPRE found that the government overruled councils fighting house builders in 17 out of 23 appeals since 2013. Matt Thomson, the CPRE’s head of planning, said developers had councils “over a barrel”. “The developers will say, ‘Either you give us the 20 per cent profit we need, otherwise we won’t build the houses’,” he said. “It’s just extortion at the end of the day.”

The charity analysed more than 60 local plans, which are council blueprints for new housing, and found that the average rural authority needed 68 per cent of new homes to be affordable. Affordable housing includes shared ownership schemes, council houses and properties owned by housing associations which are rented at no more than 80 per cent of the market rate.

In practice, the councils cut the official requirement to just 29 per cent affordable, on the ground that developers would never agree to 68 per cent. Even that has proven unachievable. Just 26 per cent of new homes in the countryside were classed as affordable over the past three years. The average rural authority is short of 46 affordable homes a year. Across 145 rural authorities in England that is a shortfall of 6,670 homes a year.

A separate report by the Institute for Public Policy Research found that 6,270 rural households became homeless in 2016, part of a 40 per cent rise in rough sleeping since 2010. The centre-left think thank partly blamed “shortages in affordable homes”.

Polly Neate, the head of Shelter, a charity for the homeless, said the crisis would only get worse “if we keep letting developers off the hook”.

The Home Builders Federation, which represents developers, said local authorities “should be realistic”. “Making projects unviable reduces overall housing supply, including the supply of more affordable housing,” Andrew Whitaker, its planning director, said.

Georgina Butler, head of affordable housing at Barratt, said the company was “absolutely committed to delivering the homes of all types that the country needs”.

A spokesman for the DCLG said almost 333,000 affordable homes had been built since 2010, more than 102,000 in rural local authorities.

A funding crisis in social housing will continue unless the government “breaks with the past” to provide financial backing for new affordable homes, the head of an influential housing sector body will say today.

Billions of pounds of taxpayers’ money could be saved by building social housing instead of channelling housing benefit to private landlords, David Orr, chief executive of the National Housing Federation, will tell the organisation’s annual conference.

The government decided in 2010 that no further public money would be made available to finance social housing, which provides accommodation at below-market rents to those on low incomes.

Britain needs to build about 250,000 new homes a year to cope with an existing shortage and a growing population, but only 141,000 homes were built last year.

About a million families are on the housing waiting list, said the NHF, which represents housing associations and social landlords.

In a report published today, the NHF says that the government is now spending “more than ever” on housing benefit to accommodate people in private rentals instead of cheaper social homes, which cost £21 a week less per person.

The amount of housing benefit channelled to private landlords almost doubled in the last decade to £9.1 billion.