Ministers facing battle over 42-day terror detention

Home Secretary Jacqui Smith said an extension of the 28-day limit was necessary because it might not give police time to question suspects in complex terrorist investigations. She also promised safeguards and said the extra time would only be used in "exceptional" circumstances.

However, Ms Smith revealed that although parliamentary approval will be required to extend a period of detention-the specific details of a case would not be discussed.

It also emerged that MPs' approval would not have to be sought until after the 42-day limit had expired.

Tory and Liberal Democrat MPs and civil liberties groups all denounced the plans today. Some warned that longer detention periods could inflame Muslim opinion and prove counterproductive in the fight against terrorism.

With a number of Labour MPs and Director of Public Prosecutions Sir Ken Macdonald also opposed, ministers risk defeat when the proposals come before Parliament next year in a new counter-terrorism Bill.

Despite this, Ms Smith told MPs: "To ensure we can prosecute people who cause murder and mayhem on our streets, we may well need to hold them longer to do that. We need to legislate now for the exceptional circumstances that there might be in the future."

Under the proposals, any bid to detain a suspect beyond 28 days would have to be authorised by the Home Secretary and recommended by the DPP and the head of the relevant police force.

In each case, continued detention would have to be approved by a senior judge and authorised again every week after the existing 28-day limit.

The Home Secretary would also have to seek the approval of Parliament, but only within 30 days of the extended time limit being enacted - which would usually be close to the end of the existing 28-day limit.

Ms Smith said only minimal details of cases requiring an extension would be given to Parliament, although a full report on each would be provided for MPs later by the independent reviewer of terrorism legislation.

Each extension will feature a " sunset clause" - meaning the power to hold suspects for extra time will expire after 60 days and would need to be renewed for any future cases.

Director of human rights group Liberty Shami Chakrabarti said ministers had abandoned attempts to build a consensus, adding: "It seems more like politics than policy-making to me."