Marbles, the credit card owned by a private-equity backed specialist subprime lender, is raising its charges in a further sign of a squeeze on consumer credit.

The 338,000 credit card accounts branded as Marbles and Beneficial were bought from HSBC by SAV Credit, which targets near-prime customers rejected by mainstream banks, for ?385m ($767m) in October.

Marbles, which accounts for most of the accounts, has traditionally catered for mainstream consumers, although the Beneficial credit card book is focused on people with poor or unusual credit records. Some of the acquired credit card customers face annual interest charges of as much as 33.9 per cent for cash advances and 26.9 per cent for purchases, when the increases come into effect next month.

SAV said the average rise would be about 4 percentage points for purchases, and 6 percentage points for cash advances. The lender said it had always intended to put up prices and was now implementing these increases. Marbles is closed to new business.

The move also reflected rising lending charges across the market in the wake of the credit crisis, it said.

However, the move will open SAV up to allegations of profiteering by the private equity industry. SAV was founded in 2001 and is backed by a private equity consortium, including Palamon Capital Partners, Electra Private Equity and Morgan Stanley Alternative Investment Partners.

The lender, an expert in the subprime market, insisted that it was simply applying its expertise to the credit card book.

Moneyfacts.co.uk, the financial comparison website, said the increase in Marbles' charges was in line with subprime credit cards.

"It is only those in real need that withdraw cash from a credit card so once again the credit crunch is hitting those who are most vulnerable," it said.

Marbles was launched in 1999 as one of the first UK online credit cards.