Leading article: Home-grown terrorism will not be stopped by these rules

But Mr Clarke's proposals are misguided. Yesterday's list was drawn up after two weeks of consultation. But the "offences" presented are still dangerously vague. The concept of "justifying" terrorism is too loose. Will it include, for example, expressions of understanding for the motivation of Palestinian suicide bombers in Israel? Problems are also raised by the concept of "fomenting" terrorist acts. What sort of activities will this include? And who will decide when a line has been crossed between legitimate propagandising and "fomenting" terror? It is likely to be left to the Home Secretary to determine the meaning of these words. This is dangerous, because it concentrates a significant amount of power in the hands of one politician.

Mr Clarke is also appropriating for himself a power that could do substantial damage to relations with Britain's law-abiding Muslim community. Under the new proposals, a database is to be created of foreign preachers and scholars accused of "encouraging" acts of terrorism in the past. These preachers will not be permitted entry to Britain. The great danger is that the Government - under pressure from the populist press - will refuse entry to respected Muslim scholars such as Yusuf al-Qaradawi and Tariq Ramadan. That will seem to confirm suspicions among some Muslims that it is not extremism, but Islam itself, that the Government wishes to target.

The Government's proposals are likely to be alienating in other ways as well. Those making public speeches and running websites will come under suspicion. Teachers, community leaders and others with responsibility for the young will be monitored. This will have the effect of curtailing free speech, and will clumsily place the entire Muslim community under suspicion. It will also be impractical because it is impossible to monitor everything that is said. Even if the Government is successful in tracking down and deporting some extremists, many more will go underground. This will make it impossible for the security services to monitor potential links between radicals and genuine terrorists.

The fundamental problem with the plan laid out by the Home Secretary yesterday is that it is not directed at the roots of extreme Islamism in Britain. The proposals affect those who come from outside the UK - asylum-seekers or radical preachers from abroad. But those involved in last month's attacks on London were British citizens. Their radicalisation seems to have taken place in local gyms, not mosques. Only one had come up on the security services' radar. This fatal lapse in intelligence should have been the primary focus of any new anti-terrorism legislation.

Terrorism will not be curtailed by deporting a handful of undesirables and banning firebrand preachers. At best, the Home Secretary's plans are irrelevant to the struggle to defeat this dangerous new breed of British terrorist. At worst, they will make eradicating murderous Islamism in the UK even more difficult.