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.