LONDON (Reuters (LSE: TRIL.L - news) ) - Newly-elected London Mayor Boris Johnson said on Thursday he was launching an investigation into his deputy Ray Lewis after allegations about his conduct were raised by the media.

Without giving details, Johnson said the allegations should be investigated but that Lewis would remain in office during the probe.

Flanked by Lewis at a press briefing at the mayor's City Hall office, Johnson said his deputy was being targeted "because he had the guts to join and serve in this administration.

"I have every confidence in Ray Lewis and I think he is a tremendous deputy mayor and a great asset to London," said Johnson.

Lewis, asked about "allegations of sexual misconduct", said they were "totally unfounded and complete rubbish".

"Those of you who know me well will know that I am not a saint but I am also not the person painted by these allegations," Lewis said.

"I've never harassed anyone, I've never defrauded anyone."

Johnson appointed Lewis as Deputy Mayor for Young People shortly after defeating incumbent Ken Livingstone for the mayoralty in May.

Lewis, born in Guyana, founded the Eastside Young Leaders Academy in 2002, which provides support for troubled young black children in London. Previously he worked as a manager in the prison service and as a church minister.

Last month Johnson's Deputy Chief of Staff James McGrath was forced to resign in a race row after he made disparaging remarks about people from the Caribbean.

(Reporting by Tim Castle)