Mervyn King, the Bank of England governor, on Wednesday said there was a “50-50” chance of inflation rising above 3 per cent during the next six months, stoking expectations of another interest rate rise this year.

If inflation were to rise to 3.1 per cent, the governor would be forced to write a letter to Gordon Brown, the chancellor, explaining why inflation had increased to such an extent and what the Bank proposed to do to ensure it came back to the target of 2 per cent.