The Government is facing an uphill battle in Parliament after unveiling plans yesterday to increase the time terror suspects can be held without charge to 42 days.

Jacqui Smith’s controversial proposal to extend precharge detention ran into a barrage of criticism from opposition politicians and civil liberties groups. The early signs from Labour backbenchers were not encouraging for government whips, with even moderate backbenchers who had rebelled on the issue before signalling that they would do so again.

George Mudie, the Labour MP for Leeds East and former Deputy Chief Whip, said: “Gordon is using up a lot of goodwill on this. It hasn’t moved me because I don’t think the evidence to move beyond 28 days is there. The House had declared its view – why come back to it?”

The Home Secretary said that an extension was necessary because 28 days might not give police enough time to question suspects in complex terrorist investigations. She insisted that the plan was “proportionate” and would only be used in the most exceptional circumstances.

There would also be “triple lock” protection under which a High Court judge, the Director of Public Prosecutions and, finally, Parliament would have to approve an extension from 28 to 42 days.

Under the proposals, the Home Secretary will be able to extend the limit immediately to 42 days after receiving a joint report from the Director of Public Prosecutions and a member of the Association of Chief Police Officers saying that it was necessary to obtain more evidence against a suspect.

Both Houses of Parliament must approve the extension within 30 days and the new limit will only be available to police for two months unless it is renewed. Individual detentions of more than 28 days would need to be approved by a judge at least every seven days and reported each time to Parliament.

However, there was concern that suspects could be held for 42 days even if Parliament eventually refused an extension. If the Home Secretary only decided on an extension towards the end of the existing 28-day limit, Parliament would not have to approve it for 30 days.

In such circumstances, a suspect could have been charged or released by the time a parliamentary vote was due. Ms Smith insisted that even if Parliament were to reject an extension to 42 days eventually, a person would still have been lawfully held.

She said that although parliamentary approval would be needed for an extension to 42 days, the specific details of a case would not be disclosed to MPs. She said of the proposal for the new powers: “If they did need to be used it would be in exceptional circumstances and where there was a proven need for it.

“It is not something we are expecting to become mundane or everyday.”

The proposals fall short of those demanded by Britain’s top police officer. Sir Ian Blair, the Metropolitan Police Commissioner, has called for a precharge detention period of between 50 and 90 days. But opposition MPs criticised the plans, saying that no evidence had been presented to support moving beyond 28 days.

Baroness Scotland of Asthal, QC, the Attorney-General, Vera Baird, QC, the Solicitor-General, and Sir Ken Macdonald, QC, the Director of Public Prosecutions, are opposed on the ground that there is no evidence to support the move.

David Davis, the Shadow Home Secretary, said: “When the Government start bamboozling like this, you know the game is up. They are making a proposal for something they still have not proved necessary.”

Nick Clegg, the Liberal Democrat home affairs spokesman, said: “It is pig-headed stubbornness for the Government to push on with extending precharge detention just as the consensus against it is deepening.

“All the so-called safeguards in this latest scheme are just a figleaf for an unwarranted extension.”

Backbench Labour MPs also signalled their opposition. David Winnick, who led the opposition to the earlier proposal for 90-day detention, said that it was “unfortunate” that ministers had returned to an issue that would simply divide MPs and peers who were united in their recognition of the threat of terrorism.

Mr Winnick said: “No evidence has been produced in my view – and in the view of a good number of other people – that any extension is necessary.”

Ian Gibson, the Labour MP for Norwich North, said that it could be a “risk too far” for Mr Brown. “With so many other things to do, this could be difficult for the Government,” he added.

Shami Chakrabarti, the director of Liberty, the civil rights group, said that the Home Secretary’s abrupt announcement had wasted much goodwill and months of so-called consensus building on national security.

“There is no evidence to extend beyond what is already the longest period in the Western world,” she said.

Eric Metcalfe, of Justice, the human rights and law reform group, said: “The UK already has a greater period of precharge detention than Zimbabwe under Robert Mugabe. The Government should be looking at reducing it, not extending it further.”

Sir Ken Jones, the President of the Association of Chief Police Officers, welcomed the proposed extension.

He said: “There is a pressing need to consider now the best way of responding to cases likely to arise in the future where the complexities of gathering evidence mean the current limit of 28 days would prove insufficient.

“These proposals address these issues alongside a careful and detailed system of checks and balances, including the requirement for agreement between a chief officer and Director of Public Prosecutions . . . before a case for an extension could be made to the Home Secretary. These provisions would only be used in exceptional circumstances.”

Times Recommends

• Times Christmas appeal: Letter from the Editor
• Conferences — what a waste of money
• Schools supremo learns a painful lesson