Extending the 28-days to a 42-day detention

Home Office minister McNulty has called on MPs to back extending detention without charge to 42 days amid growing signs the Government faces a damaging defeat on the issue.

McNulty said concerns over the proposals to upgrade from a 28-day maximum were "reasonable", but they were "proportionate" and would help with complex terrorism trials.

He insisted he was confident about steering the powers through Parliament, and stressed there was no intention of "locking people up and throwing away the key".

"I think (MPs) will buy it," Mr McNulty told BBC Radio 4's Today programme.

McNulty, Minister of State for policing, security and community safety, said the longer detention period would be used "utterly sparingly", and Parliament would be required to renew the legislation on a regular basis.

Labour's Whips are believed to have warned Gordon Brown that the Government could be defeated by around 30 votes in the Commons, if there were a debate on the 42 days now, with dozens of backbenchers - and even potentially some ministers - siding with the Tories and Lib Dems.

The Director of Public Prosecutions Sir Ken Macdonald is among a number of senior figures - including Security Minister Lord West of Spithead and ex-Attorney General Lord Goldsmith - to have voiced misgivings about the plan.

Home Secretary Jacqui Smith sought to bolster support for the proposals on Sunday by stressing the scale of the terrorist threat Britain faces.

Under the measures the Home Office would immediately be able to extend the limit to 42 days if a joint report by a Chief Constable and the Director of Public Prosecutions backed the move.