The Government is relying on an "extremely questionable" model to fund its flagship Right to Buy sell-off of housing association homes in England, a parliamentary committee has warned.

Under plans unveiled last year, local authorities will be required to sell "high-value" council homes when they become vacant, with part of the proceeds funding discounts of up to £103,900 for housing association tenants who want to buy their homes.

But the House of Commons Communities and Local Government Committee (CLGC) said the Government should pay for the scheme itself, arguing it was wrong to fund a national policy with what was effectively a "levy" on councils.

It warned that the policy could have a "detrimental" effect on the availability of affordable housing.

The amounts raised could vary widely across the country, depending on property prices locally and the number of social homes individual councils manage, warned the report.

And it said that a decision to require councils to make upfront payments would leave them at risk if homes do not become vacant at the expected rate.

Ministers say that the sums raised from selling "high-value" council homes will pay not only for Right to Buy discounts, but also for the construction of cheaper social housing to replace them and a new £1 billion Brownfield Regeneration Fund to support building on derelict land.

But the CLGC report quoted estimates from the Chartered Institute of Housing which suggested that the sale of high-value homes will raise only £1.2-2.2 billion a year of the £4.5 billion needed.

A "substantial surge" of demand to buy homes can be expected from the 1.3 million housing association tenants immediately the new scheme comes into effect, leading to the risk that the policy will "stall" for lack of funds.

Members of the cross-party committee said they were "sceptical that forcing councils to sell financially and socially valuable properties is a sustainable funding source for the Right To Buy".

And committee chairman Clive Betts said: