Borrowers who fail to maintain mortgage repayments will be given a six-month breathing space under a plan due to be announced today by the Royal Bank of Scotland.

The bank, which owns NatWest, is expected to promise not to repossess homes for six months from the date when customers first admit that they have a problem, The Times has learnt.

The move comes just days after the Government took effective control of RBS, buying 58 per cent of its shares for £15 billion. Ministers are putting heavy pressure on other British banks to consider a three-month moratorium. Repossessions have soared in recent months as the past year’s vicious financial squeeze on homebuyers has combined with rising unemployment, leaving many struggling to pay their mortgage.

In the third quarter, the number of people to have their homes repossessed leapt by 12 per cent, with 11,300 properties recovered between July and September — up from 10,100 in the second quarter, according to the Council of Mortgage Lenders.

About 168,000 borrowers are at least three months in arrears on their home loans, marking an 8 per cent rise since the end of June, the council said. It predicts a total of 45,000 repossessions this year and some economists say as many as 100,000 homes could be repossessed over the next year. The previous record was set in 1991, when the figure topped 75,000.

The RBS move is the second key concession from the banking group in days. It has also promised to maintain committed overdrafts to small firms for at least a year and not to raise overdraft rates until the end of next year.

According to one source close to the bank, it recognised that seizing properties and auctioning them would only worsen the problem of plunging house prices. Falling prices are sending millions of recent homebuyers into “negative equity” — where their homes become worth less than the mortgage.

RBS is estimated to have 17 to 18 per cent of the mortgage market and millions of home-loan customers. The Scottish bank went under government control last week, when its planned capital-raising flopped, leaving the Treasury as underwriter forced to inject £20 billion of public money.

The Bank of England is likely to cut interest rates by between a half and a full percentage point this week. But small print on many tracker mortgages, designed to move up or down in line with the bank rate, may mean many borrowers will not see their mortgage rates fall.

Ray Boulger, of John Charcol, a mortgage broker, estimates that as many as 600,000 borrowers will be affected by little-known terms of many tracker mortgage deals. A further 600,000 homeowners could also be at risk of losing out if Halifax, Britain’s biggest lender, decides to exercise its option to stop reducing tracker rates.The Council of Mortgage Lenders estimates about a third of all outstanding mortgage deals are of this type.