The Financial Conduct Authority will not begin testing firms' Mortgage Market Review processes until later in the year to allow for a "period of adjustment" while lenders and brokers get used to the new regime.
In a press briefing ahead of the formal implementation date on 26 April, Linda Woodall said it would take time for firms to get used to the more detailed advice interview but that it was to be expected.
She said: "We expect that processes which are new in the implementation phase, particularly where it involves human beings giving advice, may be slower to start off with and then the whole process will get slicker as time goes on."
Borrower interview times are expected to take two and half hours in some cases but the FCA said some of the more established larger lenders, which have been operating the MMR rules for some time, would execute the interviews quicker than others.
In a Mortgage Solutions report, brokers said they were concerned that during this 'period of adjustment' lenders would assess affordability more strictly until they got used to the rules which could lead to consumers not being treated fairly.
Woodall said that the FCA would be considering the customer experience during this time and would be contacting firms and could obtain copies of records if it thought this would be necessary to protect consumers.
"We have always said that anyone who can afford a mortgage should be able to get one," she said.
But Charles Haresnape, managing director of residential mortgages at Aldermore, said he still thinks there will be borrowers which should have been accepted by high street lenders which will be declined under the more stringent incoming rules.
He said: "Post-MMR there will be a period of adjustment. Some lenders will have tighter affordability measures than before and will restrict volume using their processes while they adapt but I think this will be a short-term measure."
But Haresnape does think longer term there will be some credit worthy borrowers which will no longer fit with a high street lender.
"I see this as an opportunity," Haresnape said. "Challenger banks and more specialised lenders which are used to using manual procedures will be able to help these borrowers."
Despite the disruption the regulator does not expect there to be a significant decline in mortgage lending as a result of the Mortgage Market Review but it expects the new rules to take some of the "froth" out of the market.
Work on the parameters of the post-implementation testing are currently under way.
