The country's most senior policeman told the Mayor of London yesterday to abandon his ambitions to exert more control over Scotland Yard.

Sir Ian Blair, the Metropolitan Police Commissioner, said that Scotland Yard had national and international roles, including leading the fight against al-Qaeda, and that these should not be stripped away to give a politician more power.

He added that it was a matter of mounting concern that the office of commissioner, which is ultimately a royal appointment, had become “a matter for high politics”.

Sir Ian's remarks followed the disclosure by The Times of e-mails in which aides of Boris Johnson, the mayor, discussed the possibility of suspending the commissioner from office pending an inquiry into his friendship with a businessman who has been awarded substantial Scotland Yard contracts.

Kit Malthouse, Mr Johnson's deputy mayor, had to be told by lawyers that he did not have the power to press “the nuclear button” and oust the commissioner. Sir Ian insisted that he got on “extremely well” with Mr Johnson but the e-mails indicated a growing rift that threatened to affect policing in London and across the country.

Mr Johnson joined Tory colleagues last year in calling for Sir Ian to resign after the Met was convicted of breaching health and safety laws over the killing of Jean Charles de Menezes, the Brazilian who was shot at Stockwell Tube station in July 2005.

The mayor takes the chairmanship of the Metropolitan Police Authority in October and has stated that he wants to accrue powers to hire and fire commissioners.

Mr Johnson's plans reflect national Conservative Party policies to exert more local political control over chief constables and police forces. Sir Ian said that he had had several conversations about the issue with Mr Johnson.

He said: “The reason the Metropolitan Police commissioner is appointed by the Home Secretary is because I have national and international responsibilities, including being the lead for counter-terrorism. There is not a single plot in the last five years that hasn't originated in or gone through London.

“It would be a poor bargain to argue that the Met should lose national and international responsibilities so the mayor can have a firmer hold over a situation which he already has power in. Most senior police officers are concerned that the office of commissioner has become a matter of high politics.”

He said he was disappointed that material about an police authority audit report into his links with Andy Miller, a management consultant who won Scotland Yard contracts worth £3million, had been leaked.

Sir Ian is facing an investigation into the award of the contracts to Mr Miller's Impact Plus company but has robustly denied any impropriety.

Mr Malthouse said: “The current legal situation was outlined to me and that process must be followed. However, I and the mayor have made no secret of our view that governance arrangements in policing are confused and lack accountability.”

Mr Johnson's office insisted yesterday that he was committed to working with the commissioner.

— Sir Ian has ordered a review of his force's charging practices for Class A drug offences after claims that there is one law for the rich and another for the poor. Hans Kristian Rausing, 45, the billionaire Tetra Pak heir, and his wife Eva, 44, were due to appear at City of Westminster Magistrates' Court to face drug charges involving crack and heroin. Prosecutors said this week that the case would be discon-tinued and that the couple would be cautioned.

Home Office guidelines state that a person's financial status can be taken into account when considering whether drugs are for their personal use.

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