Mortgage lenders are under growing pressure from the Financial Services Authority (FSA) to justify hefty exit fees as figures show that UK homeowners face £2 billion in charges should they switch deals.

In the last stage of its investigation into mortgage exit fees, the regulator has signalled that it may take action against lenders charging more than the true cost of closing a mortgage deal.

In January the FSA ordered lenders to refrain from increasing exit fees for customers who were locked into a mortgage contract. It also said that it would be “less likely to take action” against lenders that could justify their exit fees.

Now it is raising the pressure by insisting that exit fees do not exceed the true cost of closing a home loan deal, The Times has learnt. Lenders have until July 31 to comply with the FSA’s demands.

Robin Gordon Walker, of the FSA, said: “If a lender presents an exit fee as being to match the costs of the work of exiting the mortgage, he should ensure that it is just that cost and no more.

“If the cost charge is greater than the actual cost, then it is potentially a breach of the contract and could be unfair.”

Exit fees, also described as deeds fees or discharge fees, range from £50 to £295, but the true cost to lenders is around £35 according to ING Direct, the bank.

Around half of the mortgage lenders currently charging the highest exit fees — including Scarborough Building Society, Bradford & Bingley, Abbey, HBOS and Cheltenham & Gloucester — said that they were reviewing their charges before the FSA deadline.

Scarborough, which has a £245 exit fee, said: “We intend to review our exit fees and terms and conditions for future customers, in accordance with the principles set out in the FSA’s statement, by no later than July 31.”

However, Alliance & Leicester, which charges the highest exit fee in the market at £295, said that it had no plans to review its exit fees. Sally Lauder, of A&L, said: “We believe it is wrong to look at one fee in isolation. Alliance & Leicester offers very competitive all-round value products.”

Research by ING Direct shows that more than 11 million UK homeowners are paying mortgages that carry exit fees totalling £2 billion.

Mortgage firms will take £361 million for the service this year alone, against an actual cost of £67 million —a profit of £294 million, ING Direct said.