Elected mayors should not double up as police and crime commissioners, a parliamentary report has said.
The home affairs select committee also called for local police and crime panels to advise commissioners before they reach decisions, rather than scrutinise these afterwards.
Its report looked at how the Conservative policy of elected commissioners could best be introduced, not the principle behind it.
Commissioners are due to be elected in 2012, home secretary Theresa May has said, and a Bill to enact this is expected shortly.
The committee dismissed the suggestion from the New Local Government Network thinktank that elected mayors should also be commissioners.
It said the commissioner’s workload would be too large for a mayor to discharge effectively, and that handing it to an unelected deputy would defeat the purpose of increasing accountability.
MPs also cited evidence from America of the dangers of “the partiality of the mayors and their vested interests” in overseeing the police.
The report said police and crime panels should comprise mainly councillors “in particular portfolio holders with appropriate responsibilities”, together with a “significantly smaller” number of magistrates and others.
Panels should work with commissioners in advance of decisions rather than fulfil a conventional scrutiny role, the report said, arguing it would be illogical to have chief constables scrutinised by one elected commissioner and then the commissioner scrutinised in turn by a large committee.
Opponents of commissioners have raised fears that extremists and eccentrics could be elected.
But the committee dismissed this, pointing out that electorates would be so large that it was very unlikely that anyone without a mainstream party machine behind them could win.
It said senior police officers should be barred from standing for election for four years after leaving the service, so they would not be scrutinising their own decisions.
Local Government Association vice-chair Richard Kemp (Lib Dem), who gave evidence to the committee, said: “I’m delighted they seem to have supported the LGA’s positions.
“We said we would prefer the police to be scrutinised by portfolio holders from their area, but that if the government insisted on elected commissioners the panels should be dominated by councillors and work with them on decisions.
“These recommendations would make the commissioners more workable, but we will still oppose the idea.”
Association of Police Authorities chair Rob Garnham (Con) said: “The APA is fundamentally opposed to the introduction of elected commissioners, not least [because of] the very real risk of politicising police accountability through single issue elections and endangering the very fabric of the British model of policing, a model that is the envy of the world.”
He called on HM Inspectorate of Constabulary to carry out a risk assessment.