Former chief of the Prison Service Martin Narey was today appointed to investigate allegations into Boris Johnson's deputy mayor.

Mr Narey will begin looking at the claims of financial irregularity and harassment against Ray Lewis next week.

His starting point will be a dossier of evidence held by the Bishop of Barking about the deputy mayor's time as a clergyman.

However, his appointment throws up questions about conflicts of interest as Mr Narey was director general of the Prison Service when Mr Lewis was employed by the organisation. Mr Johnson's office insisted Mr Narey had no role in Mr Lewis's appointment and the two never met, but it was likely he had been aware of the younger man.

A spokesman for the Mayor denied there would be any conflict of interest over the inquiry. "Martin feels equipped to do a proper robust, independent investigation," he said.

The investigation, expected to take several weeks, will be held in private to protect the identity of witnesses and because the allegations are, to date, unproven.

Mr Johnson's spokesman said: "He'll conduct his business privately so people with learning difficulties or women who might, or might not, have been harassed don't have to have their presence in the public domain, and because these claims are unproven and highly defamatory." Mr Lewis vehemently denies the allegations.

Mr Narey will produce a report for the Mayor who will then make a decision about his deputy's future at City Hall.

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