A corruption inquiry is under way into the leaking of confidential information from Scotland Yard involving one of Britain's most senior ethnic-minority police officers.

Officers from the City of London police are investigating allegations that Met officers passed 'unauthorised' data concerning the president of the National Black Police Association, Ali Dizaei, to the Daily Mail

Several serving Met officers are thought to have been formally interviewed over claims they leaked personal details about the controversial commander who has led a high-profile campaign claiming that racism remains prevalent in the Met.

Guilty officers face disciplinary action. A Scotland Yard source said they were treating the allegations 'very seriously'. Ethnic-minority officers claimed the inquiry indicated that a 'racist' element within the Yard was attempting to smear the reputation of senior black and Asian officers.

The investigation, involving officers from the City of London police and the Met's Directorate of Professional Standards, centres on information printed in the Daily Mail about Dizaei's spending habits on his work credit card.

An article in June alleged Dizaei spent nearly £5,000 on perfume, designer clothes, expensive shoes and visits to bars and clubs on a visit to the United States. When challenged, the officer was reported to have claimed he was unaware of the rules on using his force credit card and wrote a cheque for £4,700 to cover his 'private expenditure'.

The racism row gripping the Met intensified last week with the Home Secretary, Jacqui Smith, launching a nationwide assessment of how ethnic minorities are treated and the London mayor, Boris Johnson, ordering an inquiry into the issues raised by the BPA.