Leading article: An illiberal and ill-judged move by the Prime Minister

What can explain this Government's apparent obsession with increasing the state's powers of internment? Tony Blair's attempt in 2005 to extend the time for which terror suspects can be held without charge to 90 days ended in humiliating defeat in the division lobbies of the House of Commons. The Prime Minister could not even whip his own party into supporting this outrageously draconian piece of legislation. Yet, out of nowhere, Gordon Brown announced in early 2006 that he was minded to revisit the issue. And so it came to pass when Mr Brown became Prime Minister in June. An extension of the present 28-day limit was put up for consultation in the summer. The Home Office minister Tony McNulty recently suggested that a doubling of the legal detention period to 56 days would be appropriate. And yesterday the Home Secretary, Jacqui Smith, confirmed that an extension of the period will indeed be included in the new counter-terrorism Bill.

Why is Mr Brown pushing a proposal which has been rejected once by MPs and is guaranteed to increase resentment among the Muslim communities, where its effects will be felt most strongly? The public naturally want the Government and the law to be robust in dealing with terrorists. But they are not clamouring for such an article of legislation. Nor is there any aggressive lobbying for these measures from the media. It is true that the police are in favour of an extension of the detention period. But that in itself is hardly a good reason for amending the statute book. The crucial point is that no evidence has been presented to show that the police need longer detention times in order to protect the public. As has been repeatedly pointed out, the alleged plot to blow up transatlantic airliners in the summer of 2006 was foiled without the police being forced to release any suspects prematurely.

In the absence of any convincing practical justification for such a law, we are left with the unpalatable conclusion that the Government is pushing this issue for narrow political advantage. To their credit, the Conservatives and the Liberal Democrats have been united in their opposition to this legislation since it was first proposed. Both parties have called for wire-tap evidence to be made admissible in court. This would boost the chances of successful convictions in complicated prosecution cases. If the Prime Minister truly wanted a political consensus on dealing with the terror threat through the statute book, he could have it instantly. Instead, the Government's persistence on extending detention looks very much like a crude attempt to present the opposition parties as somehow insufficiently "tough" on counter-terrorism. What makes matters still worse is the haziness of the Government's plans. Ms Smith, rather limply, admitted yesterday that the Government has "not decided" on a particular time limit for detention. If this is such an urgent and necessary piece of legislation, surely the Government's plans would be more coherent.

It is welcome that Mr Brown has dropped much of the hysterical and counter-productive rhetoric on this issue that characterised the tenure of his predecessor. The "war on terror" language has been banished. Ministers have distanced themselves from Mr Blair's ridiculous claim that "the rules of the game have changed". There is an appropriate emphasis on regaining the trust and goodwill of Muslims. But by persisting with Mr Blair's plan to extend the detention laws, Mr Brown is staining his record and draining his credibility among British Muslims. He should drop this illiberal proposal and concentrate his efforts instead on building a constructive and consensual approach to meeting the threat.