An estimated 300,000 socially rented homes could be lost in England by 2020, a housing chief has warned.
The Government's drive to boost home ownership will radically change the housing landscape across the country, MPs in the Public Accounts Committee were told.
The extension of right-to-buy to housing association tenants combined with other policies to increase owner occupancy will radically reduce the number of socially rented homes, the cross-party committee heard.
Terrie Alafat, chief executive of the Chartered Institute of Housing, told the committee: "We have done some analysis looking forward on the loss of social-rented housing, based on right-to-buy and the current policy, the proposed extension, the shift from social to affordable rent and then sales.
"And by 2020 we think there will be a loss of about 300,000-odd socially rented homes across the country.
"That is just a very top level analysis, but it does give you a sense of, over time, how much the tenure is actually changing.
"And we do need to understand better what the impact of that is, and of course in London that is going to have a particular impact because of affordability issues."
David Orr, chief executive of the National Housing Federation, said the Government is the first since 1974 not to invest any capital in new socially rented homes.
This will have a "profound impact" on housing in England, he warned.
Mr Orr told the committee: "I am anxious about the slow decline of the availability of good quality, social-rented homes - genuinely affordable homes to rent for people who are economically active but cannot afford to have their housing needs met in the market.
"This is an issue of policy in other places much more than in relation to the right to buy.
"Every government since 1974, of Left and Right, has invested at least some capital in the provision of new, social-rented homes.
"The programme that was announced in the spending review, after the present programme finishes, the new programme - apart from some supported housing - is all to support owner occupation of one kind or another.
"So this will be the first government since 1974 not to invest any capital in new supply of social-rented homes. And that will have a more profound impact over time."
He said housing associations will resort to selling housing stock to bankroll their social rents.
The committee took the unusual step of discussing the possible impact of the extension of right-to-buy while it is still being debated in Parliament.
A Department for Communities and Local Government spokesman said: "These figures are misleading and based on speculation, more council housing has been built since 2010 than in the previous 13 years.
"More homes were built as a result of Right to Buy, under the first year of the reinvigorated scheme - showing councils are delivering on their commitment to provide a new affordable property within three years.
"Furthermore we recently announced the boldest and most ambitious plan for housing in a generation backed by a doubling of the housing budget which includes delivering over 400,000 affordable homes across the country."