Don't politicise the police, Boris told

Boris Johnson is facing an angry backlash from Britain's most senior police officers over the ousting of Sir Ian Blair from Scotland Yard.

Amid fears that the appointment of Sir Ian's successor was degenerating into political warfare, The Association of Chief Police Officers (Acpo) warned the London Mayor not to seize political control over the Metropolitan Police Commissioner. Ken Jones, the Acpo president, said that Mr Johnson had created a damaging precedent that could undermine chief constables nationwide.

"I am determined that the next commissioner will be allowed to operate according to his or her judgement and ultimately the accountability will be to the law," he said. "In a day-to-day sense, the police authority clearly have a strong role ... but ultimately he or she needs to be able to stand aside from them."

Asked about the potential politicisation of the police, he added: "We are concerned, particularly at senior level. My view is chiefs and commissioners are not in a dissimilar position to judges. They need to balance vested interests, populism, and ultimately they are accountable to law. We need politicians to recognise the dilemmas they face."

As the hunt for Sir Ian's replacement began yesterday, The Independent has learnt that the deputy commissioner Sir Paul Stephenson is the Home Office's favourite to replace his former boss.

But a turf war between City Hall and the Home Office is developing as Mr Johnson made it clear he must play a key role in the selection of the head of Scotland Yard, who also leads the fight against terrorism across the country.

Jacqui Smith, the Home Secretary, has denounced the Tory mayor for effectively forcing Sir Ian's resignation, but Mr Johnson has insisted he took soundings across London – including from senior Yard figures – before telling the commissioner his time was up.

David Blunkett, the former home secretary, said: "We need to know when the new commissioner is appointed that if there was a change of government there wouldn't be a change of commissioner on the back of that, and that procedures will be followed."

Ms Smith, who has the power to hire and fire Metropolitan Police commissioners, was furious because she only learnt of Mr Johnson's decision to tell Sir Ian to go when he met her to tender his resignation on Thursday.

Mr Johnson's aides acknowledged that Ms Smith formally had the final say on the next commissioner. But they stressed that the successful candidate had to be someone who could "command the confidence of both the Home Secretary and the Mayor of London".

They dismissed reports that Mr Johnson was planning to block a permanent replacement for Sir Ian until a Conservative home secretary was in place.

Mr Johnson said that claims of a Conservative plot against Sir Ian were "completely barking" and insisted he had set no constitutional precedent when he asked Sir Ian to go. He said: "Some of the analysis I have read this morning has been absolutely outlandish. There is not and has not been any party political plot. I simply thought after long reflection that it was a good opportunity for someone else to offer new leadership, stability and increased operational effectiveness, and that was not an opportunity I could let go by."

The next Commissioner: What happens now?

*Power to appoint the new commissioner lies mainly with Jacqui Smith, the Home Secretary. A panel will assess candidates and compile a shortlist. Ms Smith will interview one or two before making her recommendation to the Queen. She will seek advice from the London Mayor and Metropolitan Police Authority. Deputy commissioner Paul Stephenson is the favourite.