Boris knifes police chief

Blair forced to quit in dramatic meeting with Mayor, provoking fury over politicisation of policing in Britain

Britain's most senior policeman was forced out of office by a Conservative mayor of London yesterday, provoking a political crisis over control of the country's largest police force.

Boris Johnson was accused of carrying out a putsch against Sir Ian Blair, who was forced to resign after being told he no longer had the confidence of the Mayor. Furious Labour ministers privately accused Mr Johnson of turning the post – which is appointed by the Home Secretary and includes leading the nationwide fight against terrorism – into a "political football". They said that Sir Ian's resignation would usher in a new era of politicised police officers.

"This makes the role of the Metropolitan Police commissioner much more political," said the former London mayor Ken Livingstone, who is a close ally of Sir Ian. "Whoever now takes the job as Sir Ian's successor will know that they may be asked to leave at a change of election." The Conservatives questioned the judgement of ministers for standing by Sir Ian for so long. His resignation ends a turbulent three-year tenure blighted by controversies.

Last year the Met was found guilty of breaking health and safety legislation over the shooting of the Brazilian electrician Jean Charles de Menezes, whose inquest could return a verdict of unlawful killing. Sir Ian was facing an investigation into the payments of millions of pounds from Scotland Yard to a friend's company. He was also facing an employment tribunal from Tarique Ghaffur, the country's most senior Asian policeman, who accused him of racial discrimination.

Mr Johnson assumed the chairmanship of the Metropolitan Police Authority (MPA) on Wednesday and immediately told Sir Ian he did not think he was the right man for the job.

After a meeting yesterday with Jacqui Smith, the Home Secretary, Sir Ian said he would quit on 1 December, the first commissioner to resign for 90 years. Mr Johnson could not sack him but as MPA head he was able to make his job untenable. In a statement, Sir Ian, 55, said: "I am resigning not because of any failures by my service and not because of the pressures of the office. I would have wished to continue to serve Londoners until my time 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. 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."

Labour sources accused Mr Johnson of "playing politics with police and terrorism" and claimed the Tories were trying to turn the MPA into a US-style supreme court, vetoing appointments.

Mr Johnson said the time had come for a "clean break and a new start for policing in London". He said he had not been influenced by any particular allegation against the commissioner, but added: "I have made it clear there comes a time in any organisation that it is right to give new leadership."