Brandon Lewis, in an answer to a written parliamentary question earlier this week, said: ‘The department has not made an estimate of the number of the most expensive third of local authority properties that will become vacant each year.’

The answer was in response to a number of questions tabled by shadow communities secretary Emma Reynolds.

The Conservative government is proposing to extend the Right to Buy to housing association tenants, funded by forcing councils to sell off homes that fall within the most expensive third of stock as they become vacant to raise £4.5bn.

The news that the DCLG has not yet estimated the number of expensive council homes that become vacant is likely to fuel further scepticism about the ability of council home sell-offs to raise enough money to fund the policy. Cash from selling expensive council stock would need to pay for a cheaper replacement council home, as well as funding the Right to Buy discounts and contributing towards a £1bn regeneration fund.

Before the election, the Conservative Party estimated that 210,000 council homes fall in the top third of expensive stock and 15,000 of these become vacant each year. Consultancy Savills in April said it was ‘highly questionable’ whether the sell-offs could raise £4.5bn.