Ministers wanted to use secret intelligence to impose a ban on a number of radical Islamic groups after the London July 7 bombings, which killed 52 people. Private e-mails from the heads of MI5 and MI6 reveal that they were reluctant to allow a repeat of the run-up to the Iraq conflict, when their assessments were used to justify the case for going to war.

Leaks of official e-mails disclosed by the New Statesman also suggest that Charles Clarke, the Home Secretary, and Jack Straw, the Foreign Secretary, were at odds, with Mr Clarke voicing doubts over the banning of some groups and suggesting that Mr Straw was “isolated” on the issue.

Inquiries by The Times have also revealed severe doubts at the top of the intelligence and security services about allowing their intelligence to be used to justify political decisions.

Senior figures have said that the wounds of the Iraq war run deep and that they should never again be used publicly to vindicate military decisions.

The e-mails suggest that John Scarlett, the head of MI6, and Eliza Manningham-Buller, his opposite number at MI5, declined to throw the weight of their organisations behind a change of policy on Islamist groups, despite pressure.

Tony Blair made the possible banning of groups such as Hizb ut-Tahrir and al-Muhajiroun part of a 12-point plan of terror measures in a press conference after the July 7 attacks and the foiled attacks of July 21.

Plans to widen the powers to ban such groups were passed in the Lords last night, although they did not specify the groups. Mr Clarke has told Parliament in a written statement that he intends to do that later.

Mr Scarlett, who was at the centre of claims that the Government “sexed up” the Iraq war intelligence and was called before the Hutton inquiry into the death of David Kelly, the weapons expert, was reported in the e-mails as saying that he “sees this as a political issue and a matter for the Foreign Secretary”.

A separate e-mail summarised the position of the agencies as being: “They do not oppose proscription but oppose reliance on their assessment to justify what they see as a change of policy, not fact.”

The e-mails apparently describe a conversation between Mr Clarke and Mr Straw on August 28. A private secretary in Mr Straw’s office quotes Mr Clarke as describing Mr Straw as isolated in his view that the political wings of the Palestinian group Hamas and Hezbollah should be banned.

The Home Secretary said that he would be “happy in principle” to include them in the overall ban but “only if the Foreign Secretary could square the agencies”. In another e-mail Mr Clarke is reported as suggesting that the Government “would lose the case for proscription”.

Mr Clarke’s apparent doubts about banning Hizb ut-Tahrir were detailed in another e-mail. But the passage that will embarrass the Government says: “There is no apparent case to proscribe HuT because its activities abroad include involvement in terrorism. Indeed, it is not entirely clear whether they would be caught under a future criterion of ‘justifying or condoning violence’.”

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