The company, Impact Plus, a business and technology consultancy, was awarded a contract with Scotland Yard in 2002. Andrew Miller, a friend of Sir Ian's, owned and ran the company.

Both Scotland Yard and the MPA have clearly stated that Britain's top police officer is not under investigation.

A spokesman for the MPA said: "MPA Internal Audit is aware of concerns about single tenders concerning Impact Plus and is currently researching the matter."

Sir Ian said: "I was open and straightforward in informing both the MPS and MPA about my friendship with Andy Miller prior to any contract being awarded. I strongly reject any suggestion that I have behaved inappropriately in any way and consider I have acted with absolute probity in these matters."

In November 2002 he sent a letter to the Treasurer of the MPA which detailed his friendship with Mr Miller.