David Cameron campaigning in 2015
David Cameron's Conservative party wants to revive Margaret Thatcher's right-to-buy policy of the 1980sGetty

More than a million families will be given the chance to buy their home at a discount, David Cameron will announce as part of the Conservative Party's general election manifesto.

The Prime Minister will present the Conservatives as the "party of working people" in an effort to secure a march on Labour only 23 days from the 7 May polling day.

The offer to let 1.3 million families buy their housing association homes at a significant discount will be funded by making councils sell off thousands of their most expensive properties as they become vacant from 2016, raising £4.5bn ($6.6bn) a year, or £18bn by the end of the parliament in 2020. While the move will prove controversial for councils and housing groups, Tory strategists hope that extending the "right to buy" will win favour among working-class voters in marginal constituencies.

The policy is being seen as a revival of Margaret Thatcher's "right to buy" scheme of the 1980s.

The pledge is expected to see tens of thousands of housing association tenants a year take up a discount on buying a housing association property, that will be capped at just over £102,700 in London and £77,000 for the rest of England.

It will also be accompanied by a requirement that councils sell their most valuable 210,000 properties from their remaining housing stock. Critics believe councils are being forced to sell their best property, and reducing council property in England into residual housing for the poor as a result.

Conservatives on a high

The Conservative manifesto will be published a day after a surprise Guardian ICM poll found the Tories surging into a six-point lead, taking David Cameron's party to 39% with Labour on 33%. Other polls had suggest that Labour was creeping ahead.

The offer on the right to buy, coupled with the proposal to cut inheritance tax trailed over the weekend, will also help counter the claim that Cameron has not set out a positive vision of a second term.

Margaret Thatcher: Titan of our time
Margaret Thatcher

The proposed discount will be worth 35% of a house, if a housing association tenant has been in the house for three years, with the value of the discount rising 1% for every extra year the tenant has rented in the public sector. In the case of a flat, the discount will be worth 50% after the first three years, rising by 2% each year afterwards.

Councils will also be required to sell about 5% of their remaining council stock. These most-valuable properties will only be sold once they became vacant, and once sold, councils will be required to build a more affordable, cheaper property on a one-for-one basis.

Opposition to the policy

The National Housing Association and the Liberal Democrats attacked the plan. David Orr, chief executive of the National Housing Federation, has previously warned that the idea of selling off social housing in "high value" areas to build more in cheaper areas is fundamentally flawed.

"It could effectively cleanse many towns of hard-working people who simply can't afford the high prices of buying or renting privately," he said.

Liberal Democrat spokesman Lord Paddick said the right-to-buy proposal would result in "longer waiting lists for homes and fewer social houses".

He said: "It does nothing to tackle the country's affordable housing needs and will only benefit the lucky few. Independent estimates suggest this could cost at least £5.8bn, nowhere near covered by forcing councils to sell off yet more housing stock, as the Conservatives suggest. That means it will have to be paid for by even more cuts hitting the most vulnerable in society."

And Ruth Davison, of the National Housing Federation, said: "We fully support the aspiration of home ownership but extending right to buy to housing associations is the wrong solution to our housing crisis."