Estate agents are already reporting delays because of the new mortgage reforms, with some first-time buyers failing the tests that lenders are now required to carry out.

The Mortgage Market Review reforms only kicked in last weekend, but some lenders and brokers were implementing the rules in the weeks beforehand.

Agent Peter Slack, of Harris Bell in Yorkshire, said: “It is absolutely right to stress-test applicants, but lenders who adopted the rules early have already had some first-time buyers fail the affordability assessment, despite the fact that they have between 10% and 15% as a deposit and an otherwise clean credit record.

“Many of these potential buyers have incomes that would have previously allowed them to obtain a mortgage, and in a few cases the proposed new mortgage is considerably less than the rent they have been paying for the last few years.”

Another agent, Ken Hume of James Alexander in south London, said: “I think the Mortgage Market Review is going to give an edge to buy-to-let investors and impede first-time buyers more than is necessary.

“We have many highly reliable tenants who have been renting for years at far higher figures than any mortgage stress-test will allow, and the equivalent mortgage would be considerably less, even taking into account any interest rate rises. The new rules could unreasonably impede many buyers who are hoping to get a step on the housing ladder now.”

According to Rightmove, over a third of people (36%) looking to buy are unaware of the MMR rules, and one-fifth do not understand them.

Matthew James, head of communications at Rightmove, said: “Should the Mortgage Market Review continue to affect a large number of applications and drive volumes down, then it could drive buyers out of the market and force sellers to moderate their prices and take some of the heat out of the current demand in some areas.”