Charles Clarke, the Home Secretary, was bounced by Tony Blair into trying to ban two Islamic parties in Britain after last year's London bombings, leaked civil service e-mails show.
The e-mails also show the heads of British intelligence refused to be drawn into a "political decision" by the Prime Minister, who announced in August that he intended to ban the radical Islamic party, Hizb-ut-Tahrir, and one of its off-shoots, as part of a 12-point anti-terrorism plan.
One highly sensitive e-mail, leaked to the New Statesman magazine, shows the Home Secretary arguing for a delay. It said: "Clarke said he would prefer putting off proscription of HuT until after the proposed amendments to the current legislation. It would, for example, be much easier to argue that HuT met the criteria of 'justifying and glorifying violence'. Clarke said his fear was that the Government would lose the case for proscription and so wanted to act cautiously."
The e-mails also reveal that Mr Clarke had described the Foreign Secretary Jack Straw, who was pushing for the ban, as "isolated".
In another e-mail, the head of MI6, John Scarlett, the man accused of having "sexed up" intelligence reports on Iraq's alleged weapons of mass destruction, is shown to be anxious not to have his agency drawn into another controversy. "He sees this as a political issue and a matter for the Foreign Secretary," the e-mail said. It went on to summarise the view of the intelligence agencies: "They do not oppose proscription but oppose reliance on their assessment to justify what they see as a change of policy not fact."
The leaks will add to the political problems Mr Clarke is having steering his Terrorism Bill through Parliament. They could set off a leak inquiry in the civil service, following e-mails also leaked to the New Statesman, showing the Government did not know if British air space had been used by the Americans to take prisoners for questioning abroad.
Shami Chakrabati, head of the civil rights organisation Liberty, said: "The e-mails show that the intelligence agencies are not going to provide cover for a political decision, and good for them. And good for Charles Clarke, because he can spot an illegality when it is waiting to happen."