Police divided over detention limit

Ministers have repeatedly cited police support for extending the period suspects may be held without trial, and Metropolitan Police Commissioner Sir Ian Blair has publicly backed the change.

Writing in The Sun newspaper, Sir Hugh Orde, Northern Ireland chief constable, also said he believed the current 28-day limit was not enough.

But The Guardian newspaper said it had spoken to four high-ranking officers who oppose the extra period.

The officers cited the damage it may do to relations with Muslim communities from which police need to gather counter-terrorism intelligence, as well as concerns over possible harm to the police's reputation and the pressure detectives may feel to find evidence against those held for 42 days.

Avon and Somerset's deputy chief constable Rob Beckley told the paper he had "doubts about the investigative need - and concerns about the impact on hearts and minds in our work with communities".

Mr Beckley, who was the Association of Chief Police Officers lead on communities and counter-terrorism from 2002-07, first went public with his concerns to a Muslim Safety Forum conference last month.

According to The Guardian, he told delegates: "It would be wrong to think that there is a uniform professional view within the police service. I, and I know other chief officers, do not see the necessity of 42 days; we can see the desirability, but at this stage I do not see the professional necessity."

But Sir Hugh told The Sun that police needed "effective and robust" legislation now to take on an "increasing" terrorist threat.

He said: "Sadly, the day will come when the number 28 is important as it will not be high enough. It may not be today or tomorrow, but we have to plan for it."