British police chiefs should not be routinely sacked at the whim of politicians, Sir Ian Blair said as he leaves his Scotland Yard office for the last time.

Sir Ian attacked the man who forced his resignation, Boris Johnson, the Conservative Mayor of London, for making “a very political move” that could destabilise the Police Service. He said that London should not become like American cities where politicians exerted huge control over police departments.

The comments by Sir Ian, in his final interview as Metropolitan Police Commissioner, come at a time when all the three main parties are planning to increase political control of the police.

The outgoing commissioner confirmed that he believed he was going to “a routine meeting” on October 1, only to be told that the mayor had lost confidence in his leadership of the country’s largest police force.

“From my point of view, he made clear that he didn’t want me to remain and it became apparent that what would happen if I stayed was we would leave the Met at war with its own [police] authority,” Sir Ian said. “I see myself as the steward of this office and it’s important if the organisation is to avoid damage for the steward to step down.”

Sir Ian added that although he had the “full backing” of Jacqui Smith, the Home Secretary, he felt that it would be impossible to stay in his job. He said: “You can’t have a position where you have a chief officer of police in a position where the chair of the [police] authority is announcing that he has insufficient confidence in him. It just does not work and I don’t know how the organisation would then have actually managed to do its business around money and policy and strategy.”

Sir Ian said he was concerned that the current political situation – in which the commissioner has to answer to a Labour Home Secretary and a Tory mayor – could destabilise the Met. He added: “It was a very political move [by Mr Johnson] and it’s kind of an imitation of New York and one of the things that does concern me is that during the 20th century I understand there were 16 Met commissioners and there were 40 [police chiefs] in New York and they came and went at the direction of the mayor.

“That’s not the British system. It doesn’t take sufficient account of the other burdens of this office in terms of national security and I hope it’s something that won’t be repeated.”

Sir Ian cautioned that his successor might be subjected to the same political turbulence. He said: “I think somebody is going to have to look at the legislation because it’s quite easy to imagine it happening exactly the other way around in four or eight years time and I don’t think that’s a good plan.”

At his final meeting of the Metropolitan Police Authority yesterday, Sir Ian confronted the mayor with his concerns. He told Mr Johnson: “Whoever comes next will need you to understand that they need your support, not uncritical but unequivocal, as is the case at every other police authority between the chief and the chair.” He added: “The job has always been difficult but I think the position that has been reached where the Home Secretary and mayor are from different parties adds a new dimension.”

Sir Ian also predicted that he would be “fully exonerated” by the inquiry into the award of Scotland Yard contracts to a friend. He admitted he had been “discourteous” in not informing a former attorney-general that he had taped their telephone conversation and that it had been unnecessary to mention the Soham murders when talking about media crime coverage.

“If, out of the thousands and thousands of column inches that have been written about me, there are three or four things that I’ve said wrong, well, OK, but I’m not superhuman,” he said.

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