Ministers have paved the way for further concessions on plans to hold terrorist suspects for up to 42 days without charge in an attempt to avert another rebellion by Labour MPs.

A leaked paper suggested that the Home Office was considering giving judges the power to order that terrorism suspects be released with an electronic tag or on bail as an alternative to detention. Gordon Brown would be able to claim that this meets his aim of giving police up to 42 days between arresting a suspect and charging or releasing them. Further concessions are also expected, with an offer to shorten the period within which Parliament must debate the extended powers of precharge detention if they are invoked.

Downing Street sources said yesterday that there would be “no concessions on the fundamentals of 42 days”, although they conceded that there would be debate on the mechanics. The Home Office said that it had all along included “the option of increasing the involvement of judges in precharge detention”, which Lord Carlile of Berriew, the independent reviewer of antiterrorism legislation, had advocated.

Mr Brown has until mid-June, the date pencilled in for the report stage and third reading of the Counter-Terrorism Bill, to win over a chunk of the Labour MPs – there are up to 50 – who oppose his plan to extend the maximum period of precharge detention from 28 days. Yesterday on BBC Radio 4 Jack Straw, the Justice Secretary, told The World This Weekend that Jacqui Smith, the Home Secretary, “will carry on listening because that is the nature of the individual”.

Ministers had claimed that the new powers were intended to be reserved for the most serious terrorism investigations. According to a Home Office document published by The Sunday Times, ministers were told that conceding that suspects be freed on bail or with tags “would be resisted by [the] Crown Prosecution Service and police”.

The Home Office refused to comment on the suggestions, saying that it did not discuss leaked documents, but a spokesman said: “The Government has repeatedly outlined its willingness to seek consensus on this proposal and we have consulted widely.”

Holding pattern

How a terror suspect could be held for 42 days:

— Suspect(s) arrested in “exceptional” terror inquiry, ie multiple plots that cover several countries, or are unusually complex

— Joint report by police and prosecutors says that there is a compelling operational need to hold suspect(s) beyond 28 days without charge

— Ministers sign commencement order to trigger reserve powers. Home Secretary must tell Parliament that she has done so within two days or as soon as practicable

— Suspect(s) brought before judge, who decides whether to allow the detention to continue at seven-day intervals up to 42 days

— Parliament must then give approval for reserve powers within 30 days, with MPs recalled in recess if necessary. Reserve powers remain for 60 days

— Police must charge or release suspect(s) after 42 days

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