He said: "To deal with the challenge posed by the terrorist threat we have to do more, working with communities in our country, first, to challenge extremist propaganda and support alternative voices; and secondly, to disrupt the promoters of violent extremism." The Home Office says preventing radicalisation is the key weapon in its armoury against home-grown terrorism.

Why, then, is a radical Lebanese propagandist with links to the extremist group Hezbollah on a speaking tour of Britain? Ibrahim Moussawi edits Hezbollah's newspaper and is former political editor of its television station, which is banned in many countries including France, Spain and America as its output is seen as anti-Semitic.

He was recently barred from entering Ireland, where he was due to speak at anti-war meetings. But over the past few days he has addressed rallies in London, Bristol, Birmingham, Manchester, Norwich and Cambridge.

Tonight he is due in Cardiff. I have not attended any of these events, so for all I know Mr Moussawi has regaled his audiences with denunciations of jihadism and praise for the democratic way. He is certainly availing himself of one of the latter's most precious commodities, freedom of speech.

Mr Brown himself has set out the circumstances in which he considers that it is right to circumscribe such freedom. It is bad enough that human rights laws prevent us ejecting foreign nationals who wish us harm; but it is open to the Home Office to exclude from Britain any foreign national whose presence here is not conducive to the public good.

Mr Moussawi is unlikely to use his platform to foment extremism or to promote violence while he is here and he no longer works for the television station. It could be argued that stopping him touring the country at the invitation of the Stop the War coalition could play into the hands of those who accuse the West of shutting down discussion about the issues raised by the Iraq invasion or the problems in the Middle East.

Yet there might also be an impressionable young Muslim in his audience, burning with resentment against Western foreign policy, who will regard this representative of an extremist movement as a role model.

Why, when it is possible politely to decline Mr Moussawi's application for a visa, run the risk of radicalising one more individual? The Home Office says it "does not comment on individual cases" so finding out the thinking behind the decision is impossible.

This case reflects the confusion and a lack of transparency at the heart of the Government's counter-radicalisation strategy. Something called the Preventing Violent Extremism Pathfinder Fund is meant to direct £45 million towards 200 projects in 70 local council areas which ministers say will help counteract jihadi and separatist propaganda. It will dispense £6 million this year; but finding out precisely where the money is going has proved surprisingly difficult.

Paul Goodman, the MP for High Wycombe and the Conservative communities spokesman, asked for the information last August and has only recently received a full reply. The programmes include a high number of sports schemes; others include English courses for imams and anti-extremism seminars. Inevitably, nearly all the groups in receipt of money are Muslim organisations.

When Hazel Blears, the Communities Secretary, was asked in the Commons whether she could guarantee that none of this money has ended up with extremist groups she conceded that, while it was important to "monitor very carefully indeed the groups to which this money is allocated", this had not yet been done centrally because the money was being channelled through local authorities.

It is clear from the list given to Mr Goodman that some of the organisations in receipt of funding are controversial. They include the Cordoba Foundation, which has received £19,000 from Tower Hamlets to organise a series of debates, including one with Hizb-ut-Tahrir, a group that Tony Blair once threatened to ban.

The Cordoba Foundation was founded by the prominent British Muslim Anas al-Tikriti, former president of the Muslim Association of Britain (MAB) and the son of the leader of the theocratic Muslim Brotherhood in Iraq. Members of the MAB have previously indicated their links with Hamas and their support for suicide bombings abroad.

Another beneficiary of the fund is the Islamic Foundation, which was described by Panorama as one of "the most influential" outposts of "militant Islamist ideology" in Europe. Other recipients include Birmingham's Green Lane and Central mosques, which featured in an undercover Channel Four Dispatches programme in which imams were recorded making inflammatory, though not, said the police, unlawful comments.

In a new book, Human Being to Human Bomb, Russell Razzaque, a Muslim psychiatrist - who as a student experienced extremist Islam - sets out how seemingly "ordinary" and well-adjusted young men can rapidly fall under the jihadi spell. He believes that there is a "conveyor belt" of particular personality types who can be identified early and diverted from the path that could lead to disaster.

While establishing a fund to challenge extremist propaganda might be a proper use for public money, the funding must go to the right people. To ensure that it does, it must be possible, surely, to compile a list of organisations that should not be given taxpayers' money under any circumstances.

As Miss Blears said: "We must ensure that we fund groups who absolutely stand up and condemn terrorism and want to participate in tackling it." It would certainly be extraordinary if our money were financing organisations that do the exact opposite, though no more odd than allowing into the country individuals who lend their support abroad to those engaged in the sort of activity that we are trying to prevent here.