Lib Dem leader says prime minister is ‘choosing to turn a blind eye and ignore the most vulnerable people in Britain’

David Cameron will be guilty of presiding over the death of social housing if controversial plans to force the sale of council houses to pay for an extension of the right to buy programme to housing associations are left unchanged, Tim Farron has said.

The Liberal Democrat leader warned that the “all-out assault” on social and affordable housing could destroy 30 years of work in rebuilding the housing stock.

Farron will say: “Millions of people are living in fear and desperation because they have no secure place to call home. Yet Cameron is choosing to turn a blind eye and ignore the most vulnerable people in Britain.

“Cameron is now attempting to do what he could never do before – to launch an all-out assault on social and affordable housing. If his plans go through unaltered he will destroy in just six months what has taken thirty years to rebuild since Thatcher. This will be death of social housing as we know it.”

Farron spoke out after the government reached agreement with housing associations and the National Housing Federation that will see the right to buy scheme extended to an extra 1.3 million families.

The Local Government Association (LGA) criticised the “secret” deal agreed last month, which saw housing associations drop their objections to the scheme after securing the right to opt out of offering properties for sale to tenants if they have a strong reason to do so.

The LGA told the Observer that the scheme marked “a move away from providing the genuinely affordable homes the most vulnerable in our communities need”.

The controversial housing policy was one of the main features of the Conservatives’ general election manifesto. The Tories pledged to extend Margaret Thatcher’s landmark right to buy initiative, which allowed tenants in council houses to buy their properties at a discount, to housing association properties. This will be funded by obliging councils to sell off their most expensive properties.

Facebook Twitter Pinterest Council flats in Islington, London. Photograph: Alamy

Farron said: “The plans will provide a lottery ticket for the lucky few, but the ladder will be pulled up behind them. For the majority of people who can’t afford a deposit it will make things even worse.

“I will speak up on behalf of those who will be tossed aside by the government under these plans. Everyone deserves a decent home and the security to know that no one can take it away from them.

“We are moments away from what can only be called a housing disaster. We will look back in generations to come and see just how significant these Tory changes are.”

The Lib Dems are so incensed by the government’s plans that 10 of the party’s most prominent leaders in local government have warned that the government’s plans risk exacerbating a national emergency on housing.

In a letter to the Guardian the group, led by the mayor of Watford Dorothy Thornhill – who is also the party’s local government spokesperson, they write: “We are outraged at the government’s short-sightedness in selling off council homes to pay for the right to buy extension to housing associations.

“We have a vast shortage of affordable homes, which constitutes nothing short of a national emergency, and yet the government is seeking to make quick financial gains by disposing of properties which could provide much needed homes for generations.

“Forcing right to buy on housing associations was the wrong policy before the election, and it remains the wrong policy now. Shifting homes from one tenure to another without addressing our failure to build enough homes overall is like rearranging the deck chairs on a sinking ship.”