David Cameron's flagship plan to extend the right to buy to 1.3 million housing association tenants could be implemented voluntarily under plans to be considered by ministers.
The National Housing Federation (NHF) - the trade body for the associations - said it had put forward proposals which would mean that they would not be forced to sell homes to tenants through legislation.
The Department for Communities and Local Government (DCLG) said it would look at the plan but denied that it represented a watering down of the Conservatives' general election manifesto pledge.
A Government spokesman insisted they were committed to ensuring all tenants had the chance to buy their home and that associations would be compelled to sell if they refused to do so.
The promise to give housing association tenants in England the right to purchase their properties at a discount under the same terms as council tenants was a plank of the Tories' election campaign - echoing Margaret Thatcher's original right-to-buy policy.
Under the NHF proposals the discount received by the tenants would be fully funded by the Government and every property sold would be replaced by another housing association home.
"Crucially, as the associations would not be compelled to sell stock under legislation, but entering an arrangement voluntarily with Government, the independence of the sector would be maintained," the NHF said in a statement.
The proposal depends on the NHF's 1,100 member associations being prepared to accept the plan - with a deadline of just one week to decide - but chief executive David Orr said he was "confident" that they would do so.
"Housing associations have always been committed to helping their tenants get on in life, whether that's finding a job or buying their first home. So we are urging our members to sign up to work with government to deliver this new right-to-buy proposal," he said.
Earlier, addressing the NHF conference in Birmingham, Communities Secretary Greg Clark said that the proposals represented an "historic change".
"In keeping with the housing association tradition to empower and meet the needs of their tenants, associations would give the chance - not just of some of your tenants, but to every one who wishes to take it - to own their own home," he said.
A DCLG spokesman said: "The NHF have voluntarily come forward with a proposal, which the Government will now consider."
A Government spokesman rejected claims that the move represented a dilution of the manifesto commitment.
"This isn't true. Our manifesto commitments remains the same," the spokesman said.
"Housing associations will have the chance to comply with our right-to-buy policy. But if they fail to do so, we will bring forward measures forcing them to offer it to tenants."