Right-to-buy was first introduced in 1980 under Margaret Thatcher, giving council house tenants discounts to buy their own home.
Although Labour subsequently dropped its opposition to the policy in 1999 the discount was reduced from £50,000 to £38,000.
To fund the cost of 4.5bn annual cost of the scheme councils will be forced to sell off their most valuable 210,000 social homes as soon as they became vacant.
Cameron said: "The next Conservative government will extend the right-to-buy to all housing association tenants in this country – 1.3million extra families – a new generation given the security of a home of their own."
The original right-to-buy saw more than 1.5million council homes being sold off at discounted rates. Leading to a surge in home ownership, it became Lady Thatcher's most famous single policy.
The extension of right-to-buy has received backing from within the industry, however most think the policy ignores the problem of a lack of housebuilding which a new government should prioritise.
Brian Murphy, head of lending at the Mortgage Advice Bureau, said: “The Conservative pledge of an extension to the Right to Buy scheme will undoubtedly come as good news to the 1.3 million families living in social housing.
“However, this is no fix-all solution to Britain’s long-term housing needs. The move will help social housing tenants to get on the housing ladder, but will do little to provide a much needed boost to UK housebuilding or ease the concerns of families looking to buy who are living in private rental accommodation.”
And Patrick Bamford, director – Mortgage Insurance Europe for Genworth, said: “While welcome for those families, [it] tackles just a small part of the problem in the housing market.
“The policy fails to do anything for the millions of other hopeful first-time buyers that are still struggling to save enough to get a foot on the property ladder.
“It neglects the fundamental problem at the heart of the affordability crisis, which is that limited house building is restricting supply and pushing prices up further at a time when traditional first time buyer mortgages are still hard to come by.”
The Royal Institution of Chartered Surveyors is especially critical of right-to-buy’s extension, as its head of policy Jeremy Blackburn, said: “Extending the right-to-buy policy to housing associations and selling our remaining council housing stock is not a responsible approach to addressing the housing deficit.
“If proceeds from these are to pay for new build, owner-occupied houses on brownfield sites, it is not a workable policy that delivers across all tenures.
“A brownfield fund has the potential for unlocking land supply to build more houses in the next Parliament and is a welcome commitment from the Prime Minister. However, for this to replenish public housing, the proceeds must fund like-for-like replacements.”
