A debt charity has accused Northern Rock, the nationalised mortgage lender, of "aggressively" pursuing homeowners who are struggling to meet their mortgage repayments for the money they owe.

Credit Action said Northern Rock has an "inflexible" approach to borrowers who fall into arrears and is seeking to repossess homes too quickly.

In the first half of 2008 there were 19,000 repossessions, according to the Council of Mortgage Lending (CML). At the end of September, Northern Rock had a stock of 4,200 seized homes.

Chris Tapp, the director of Credit Action, said the bank was under pressure from the Government to pay back a huge amount of debt to the taxpayer. "Northern Rock has a very inflexible approach to borrowers who fall behind with repayments. Borrowers who are making full repayments but are unable to pay back arrears going back a few months are being actively pursued in the courts."

He added: “They are being quite aggressive in terms of their use of the courts in going for repossession, but for a lot of people they don’t need to get to that point, if only Northern Rock would be more flexible with them in the first place."

"The Government needs to use its leverage to ensure that repossession is the very last resorts."

There are growing numbers of borrowers struggling to make their mortgage repayments, according to figures. CML found that 1.33 per cent of borrowers were in arrears of up to 3 months with their mortgage in the first quarter of this year, a jump of around a third compared to the same period last year.

When Northern Rock was nationalised in February, it had a stated aim to reduce the size of its loan book and has written to customers coming to the end of fixed-rate deals suggesting they remortgage elsewhere.

To encourage new and existing borrowers to look at other lenders, Northern Rock has also maintained uncompetitive rates.

Borrowers who took out mortgages worth up to 125 per cent of the value of their home have found that they are unable to remortgage elsewhere and are forced to remain on Northern Rock's standard variable rate, which is one of the highest from the mainstream lenders, at 7.34 per cent.

Last week, following the 0.5 percentage point fall in the base rate, the Rock cut its SVR by 0.15 percentage points.

Figures from the Ministry of Justice show that there were 30,220 orders made for repossession in the second quarter of this year, around a 30 per cent jump compared to the same period last year.

Mr Tapp said he was concerned that there were fears that other lenders who had been part-nationalised, including Halifax, the Britain's biggest lender, would be encouraged to pursue a similar policy. "There is concern that this will also be the attitude amongst the management of these part-nationalised lenders, who will be keen to keep the levels of bad debt on their balance sheets low."

Simon Hall, a spokesman for Northern Rock, said: "We refute any suggestion that we have an aggressive stance towards repossession".

He pointed out that mortgage arrears had increased across the sector as a whole. He also said that figure of 4,000 was inaccurate as it referred to the number of unsold repossessed homes it had on its books at the end of September, not the number of repossessions in total in the first six months of the year.