by Francesco Guerrera, Saskia Scholtes  and Tom Braithwaite

Published: June 30 2009 23:59 | Last updated: June 30 2009 23:59

Citigroup has sharply increased interest rates on up to 15m US credit card accounts just months before curbs on such rises come into effect, in a move that could fuel political anger at the treatment of consumers by bailed-out banks.

People close to the situation said that Citi, which is about to cede a 34 per cent stake to the US government as part of its latest rescue, had upped rates on between 13m and 15m credit cards it co-brands with retailers such as Sears.

Citi's rate increases emerged on the day the government proposed legislation to create a new regulator with sweeping powers on consumer protection and a week after the bank was attacked by some politicians for raising employees' salaries.

Holders of co-branded cards who failed to pay their balance in full at the end of the month saw their rates rise by an average 24 per cent - or nearly 3 percentage points - between January and April, according to a Credit Suisse analysis of data from the consultancy Lightspeed Research.

After FT.com broke news of the hike, Citi issued a statement saying: "We have adjusted pricing and card terms for some customers as part of our regular account reviews. This is an ongoing process to ensure we offer terms, interest rates, credit lines and products based on individual needs and risk profiles. These changes also reflect the dramatically higher cost of doing business in our industry as we work to preserve the broad availability of credit."

Citi's move came as the economic downturn caused record defaults among US card users and prompted many issuers to raise rates, both to cushion their losses and pre-empt the new restrictions set to come into effect in February.

However, Citi's increases have been larger than those of its main rivals, according to Lightspeed, which tracks about 12,000 US credit card accounts.

Carolyn Maloney, Democratic representative for New York, the author of the new rules that will sharply constrain lenders' ability to raise rates for risky borrowers, criticised Citi's move. "It's hard to tell if rate hikes on existing balances being put in place now are the result of prior bad business decisions or getting in under the wire of the new law," Ms Maloney told the Financial Times.