The investigation has been jointly agreed with the Prudential Regulation Authority and the Financial Conduct Authority, the Treasury said in a statement on Friday.

"It will be led by an independent person appointed by the regulators, with the approval of the Treasury," the finance ministry said.

The investigation won't start until it is clear it will not prejudice any actions the two regulators may take, it added.

(Reporting by Huw Jones and Matt Scuffham)