The Right to Buy scheme will be extended to housing association tenants if the Conservatives win the next general election.

According to prime minister David Cameron, this will enable the scheme to be opened up to a further 1.3 million families.

This, he said, means that a "whole new generation "will be "given the security of a home", with people who have worked hard and saved able to own the house they live in.

Mr Cameron unveiled the policy at the launch of the Conservative's general election manifesto, which he said shows it is "the party of working people".

However, the idea has been criticised by the Liberal Democrats, which said it was "full of flaws" and likely to lead to longer waiting lists for homes.

The party is also concerned that extending the Right to Buy scheme in this way could trigger a fall in the number of social houses available, as well as do nothing to "tackle the country's affordable housing needs".

Figures cited by the Liberal Democrats indicate the measure could cost in the region of £5.8 billion.

This, it said, would be "nowhere near covered by forcing councils to sell off yet more housing stock, as the Conservatives suggest".

The Liberal Democrats added that it would therefore need to be paid for "by even more cuts hitting the most vulnerable in society".

However, home secretary Theresa May has responded to criticism of the policy by telling BBC Radio 4's Today programme by insisting it will not increase the shortage of social housing.

Andrew Murray, a partner at Winckworth Sherwood Solicitors, commented: "Unless registered providers are compensated for the entire value of the discount, there seems to be a substantial risk of legal challenge if the policy is implemented."