US politicians have renewed calls for stricter financial regulation in the wake of America's biggest bank revealing a surprise $2billion (£1.2bn) trading loss.

JP Morgan Chase claimed the loss by one of its trading groups, revealed last Thursday, was the result of a strategy to manage financial risk. But critics said it was more likely to have come from risky bets.

Simon Johnson, former chief economist for the IMF, said: "It just shows they can't manage risk – and if JPMorgan can't, no-one can."