Metropolitan Police Commissioner Sir Ian Blair, who has been dogged by controversy, has announced he is quitting his job. Sir Ian, 55, who will step down on December 1, was criticised over the killing of Jean Charles de Menezes, his handling of a racism dispute with his most senior Asian officer and is also under investigation over police contracts awarded to an associate. He said he is stepping down 16 months before his five-year contract was due to expire because he felt he had insufficient backing, including from London Mayor, Boris Johnson. Sir Paul Stephenson, his deputy, will take over until a successor is appointed. Sir Ian said: "I am resigning in the best interests of the people of London and the Metropolitan Police Service. I would have wished to continue to serve Londoners until my term of office expired in February 2010. "However, at a meeting yesterday, the new Mayor made clear, in a very pleasant but determined way, that he wished there to be a change of leadership at the Met. I understand that to serve effectively the Commissioner must have the confidence of both the Mayor and the Home Secretary. "Without the Mayor's backing, I do not consider that I can continue in the job. Personally I see no bar to working effectively with the new Mayor, but it is there that we differ and hence I am unable to continue." Home Secretary Jacqui Smith said she had accepted the resignation "with regret" and paid tribute to his work fighting crime in London and tackling terrorism across the country. She said: "Sir Ian can be proud of his contribution nationally and locally. He has transformed the police's capacity to prevent and deal with terrorism throughout Britain, including his leadership during terrorist outrages on London streets." Mr de Menezes, an innocent Brazilian, was gunned down by police at Stockwell Tube Station on July 22, 2005, when the capital was on alert following the suicide bombings which killed dozens of people two weeks earlier. A six-month investigation was held by the Independent Police Complaints Commission, whose most damaging criticisms were reserved for Sir Ian. He was accused of causing "much of the avoidable difficulty" after the shooting - referring to his decision to block IPCC investigators for three days. Sir Ian - who defied his critics by refusing to resign and survived a vote of confidence several weeks later - is now being probed for allegedly using public money to pay a close friend, Andy Miller, a five-figure sum to improve his image when he was Deputy Metropolitan Police Commissioner. Contracts were allegedly awarded to Impact Plus, a company owned by Mr Miller, to make over his communications strategy and leadership style. According to reports, Sir Ronnie Flanagan, HM Chief Inspector of Constabulary, briefed members of the Metropolitan Police Authority about the so-called "vanity contract" payments - understood to be worth more than £15,000. Sir Ian, who became the Met chief in February 2005, has previously rejected the suggestion he "behaved inappropriately" on the issue. In a further controversy, Sir Ian effectively suspended Assistant Commissioner Tarique Ghaffur last month after the country's top Asian policeman held a press conference to outline his racial discrimination claims against the Metropolitan Police. One of the favourites to succeed Sir Ian is the Chief Constable of the Police Service of Northern Ireland, Sir Hugh Orde. However, Sir Hugh said: "I've only just been made aware that some statement is going to be made and, as I said at today's board meeting, my concern currently is to protect the community of Northern Ireland and to deal with the dissident republican threat and that is where 100 per cent of my energy currently is." He added: "I have two years of my contract left here, I have no plans to move at the moment - wait and see I suspect is the best answer to this."