Council leaders have warned that any homes sold under the newly-extended Right to Buy scheme must be replaced on a like-for-like basis.
Today Prime Minister Boris Johnson announced that up to 2.5 million housing association tenants will be given the right to buy them outright.
Mr Johnson pledged that for every home sold - which will be offered up to 70% off the market value - one new social home would be built.
But the Local Government Association (LGA) warned the number of new council homes being sold was already not keeping pace with the current Right to Buy scheme.
LGA housing spokesperson, David Renard, said: 'Any houses sold must be replaced quickly, in the same local authority area and on a like-for-like basis.
'Equally, the cost of discounts must not be funded from the sale of council housing stock nor be met from existing Government funding commitments for delivery of additional affordable homes.'
Chair of the Levelling Up, Housing and Communities Committee, Clive Betts, added: 'The Prime Minister needs to make clear that, if the Government presses ahead with extending Right to Buy for those renting housing association properties, it is vital the money goes back into the system of social housing so that new homes can be made available for low-cost rent and purchase.'