Boris Johnson signalled his desire yesterday to remove Sir Ian Blair as Metropolitan Police Commissioner if he is elected mayor of London.

Mr Johnson said that he would have to have “a working relationship” with Sir Ian if he won the May 1 election, only because he would not have the power to dismiss him.

He said that the next head of Scotland Yard should either be appointed by the mayor or elected. Mr Johnson also confirmed that he would assume the chairmanship of the Metropolitan Police Authority (MPA) if he wins.

Last year Conservative members of the authority voted in favour of a motion of no-confidence in Sir Ian after the Met’s conviction for health and safety breaches in the Jean Charles de Menezes case. Sir Ian survived the leadership crisis – with the backing of the Home Office and Ken Livingstone, the Mayor – but Mr Johnson was one of the leading Tories clamouring for him to step down.

In his crime manifesto, Mr Johnson declared that the leadership of the Met was out of touch, and that he would “get directly involved with the day-to-day scrutiny of the police and get more officers on the streets”.

But he refused to say how he would vote if he were the MPA chairman in another confidence motion.

He said: “I’m going to have to have confidence in his leadership of the Met insofar as I can’t remove him. I do think they [the Met] need a yank on the steering wheel and that’s what I intend to provide.”

Sir Ian became Commissioner in February 2005 for an expected five years. Although his leadership has been dogged by controversy, crime in the capital has fallen steadily.

According to official figures, total recorded crime fell by 6.1 per cent in 2007, violent offences were down by 5.3 per cent and homicides fell from 172 in 2006 to 160 in 2007.

Mr Johnson said the commissioner’s office should be stripped of its national responsibilities for counter-terrorism and be confined to policing London. He said a separate national counter-terrorism police force should be independent of Scotland Yard.

The Conservative candidate said that tackling crime was the corner-stone of his mayoral campaign. He would establish a crime-mapping website that would allow Londoners to see the exact level of criminal actitivity where they lived and to raise specific issues with police.

Mr Johnson also pledged to cut crime on the public transport network – removing the right to free travel from teenagers who committed offences on buses and banning consumption of alcohol on Tube trains.

A mayor’s fund would provide support to voluntary sector organisations working to combat gang culture.

Mr Johnson said: “You are more likely to be mugged or assaulted in London than you are in New York. There is an epidemic of unreported crime and people feel an increasing sense of detachment from the police. I want to change that.”

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