Research by the Home Builders Federation shows around 8,500 affordable homes due for completion in the next 12 months could be left without occupants because registered providers are no longer taking them on.

At least 900 already-completed homes are currently standing empty.

Section 106 agreements, which underpin almost half of all affordable housing delivery, rely on housing associations purchasing discounted units from developers.

But a “perfect storm” of economic pressures and policy uncertainty has seen providers pull back, leaving projects stranded and undermining the Government’s five-year housing plan.

Ninety HBF members have signed a letter to the housing minister warning that without urgent action, thousands of homes will remain unbuilt or empty.

They called for greater use of “cascade mechanisms” to allow stalled affordable homes to be switched to other tenures, or for cash payments to councils in lieu of provision.

Neil Jefferson, chief executive of the HBF, said: “Against rising affordability pressures and increasing numbers of families living in temporary accommodation, it cannot be that Affordable Homes are left standing empty.

“Government’s social and Affordable Housing announcements were a welcome step to giving Registered Providers confidence to plan long term, but they are doing little to ease the immediate constraints of delivering affordable housing through Section 106 agreements.

“Right now, an estimated 100,000 private units are stalled, which not only threatens the supply of much-needed homes but also risks the livelihoods of regional businesses and hardworking tradespeople up and down the country.

“While Government’s housing announcements have been welcome, as it stands, housing associations are unable to bid and private buyers unable to buy, leaving the housing outlook increasingly uncertain.”