David Coughlin, of the Landlord Sales Agency, said that many good landlords had frozen rents for years as tenants faced cost-of-living pressures, but had now been forced to sell up.
He added: “In the past six months, the market has gone bananas ahead of the reforms. You’ve got landlords who now can’t increase rents, so they’re having to sell at a massive discount.”
The problem landlord exodus has been particularly acute in the capital. Around 30pc of London homes for sale in the 12 months to March were formerly buy-to-lets, compared with 13pc across the country, according to analysis by estate agency Savills.
Jessica Tomlinson, of Savills, said that as a result, renters in outer London were more likely to be affected by a lack of supply.
She added: “In prime central London, much of the rental stock is owned by large estates or long-term international investors. Many of these are better able to weather additional legislative and regulatory changes, therefore limiting stock shortages.
“By contrast, in outer London, a higher proportion of properties are held by smaller buy-to-let owners and accidental landlords who will be more likely to be impacted by upcoming changes.”
A Ministry of Housing, Communities and Local Government spokesman said: “Our landmark Renters’ Rights Act protects renters from excessive rent increases by limiting rises to once a year, allowing tenants to challenge above-market increases and banning rental bidding wars.
“There is no evidence our reforms are driving landlords from the sector, and good landlords have nothing to fear.”