A four-year investigation into a top Asian police officer collapsed yesterday, leaving taxpayers with a bill of up to £5 million.

Superintendent Ali Dizaei - who had been tipped to become Britain's first black chief constable - said: "I find it astonishing and extraordinary that taxpayers' hard-earned funds could be abused in this way."

The development has plunged the Met into a fresh race relations row, the Guardian reports today.