Altaf Hussain is far from being the only foreign dissident to set up shop in London in recent years. The capital has become one of the world's leading havens for dissidents and exiled politicians, particularly from Islamic countries.

Dissidents flock to London because Britain's asylum laws, unlike those of other European countries, do not curb the political activities of those allowed to take refuge here.

One of the most controversial dissidents currently in Britain is Rashid Ghannouchi, leader of the banned Tunisian Islamist party, the Nahdha, who has been convicted in his country on terrorist charges, including the masterminding of a bomb attack on a hotel in which a British tourist lost a foot.

A particular thorn in the Government's flesh is the presence here of dissidents campaigning against friendly Arab governments in the Gulf. These include Mohammed al-Mas'ari, a Saudi fundamentalist academic who is working for the overthrow of the Saudi monarchy. With nearly 30,000 jobs at stake in the pounds 20bn al-Yamamah arms contract, the Government is keen to distance itself from Dr Mas'ari. John Major recently told Arab envoys in London that the Government gave no encouragement to his activities.

Other extreme Arab groups operating in London include Hamas, the radical Palestinian group, and the Algerian Islamic Salvation Front (FIS). Both France and Israel have protested strongly about their presence here.

Concerned by Britain's growing reputation in the Middle East as a haven for terrorists, the Government has considered tightening Britain's asylum laws. But the Home Office is unwilling to change the criteria for admission and is loth to undermine Britain's reputation for fair dealing by making asylum dependent on politically acceptable views.

In any case, some dissident groups have a good relationship with the authorities. The two main Iraqi groups in London, the Free Iraqi Council and the Supreme Council for the Islamic Resistance in Iraq, both foment "terrorist" activity inside their homeland, thus contravening the asylum laws. Yet the Foreign Office remains in close touch with both groups, whose leaders regularly pop in and out of Whitehall offices.