However, only a few dozen members of al-Muhajiroun turned up at Trafalgar Square for the meeting.

They were greeted by rival protests from extreme right wing and communist groups.

The Greater London Authority (GLA) had refused permission for the rally but did not have the power to ban it.

Terrorist warning

A GLA spokeswoman said: "We have received complaints in past years that al-Muhajiroun was using the rally as a platform for its anti-Jewish and homophobic opinions."

Al-Muhajiroun leader Sheikh Omar Bakri Mohammed also addressed the crowd

The rally was addressed by group leader Sheikh Omar Bakri Mohammed, a radical who recently warned the UK of terrorist attacks if it joined military action against Iraq.

Sheikh Abu Hamza, leader of the Finsbury Park Mosque, also addressed the crowd.

One of the organisers of the rally, Jim Choudhury, told BBC Radio 5 Live the group "had a right" to stage the rally, which was meant to support the Islamic religion.

"It's an Islamic duty upon every Muslim to call on the society in which he lives to embrace Islam as an ideology.

"The rally for Islam is intended to concentrate on people who are thinking about Islam, or want to know more about Islam, and to dispel some of the misconceptions that people already hold about Islam and Muslims."

He denied the group was homophobic or anti-Semitic - although he conceded he believed homosexuality was "an abomination".

The people who form al-Qaeda or the Taleban happen to be Muslims so inevitably every Muslim will have something in common with them

Organiser Jim Choudhury

"Al-Muhajiroun are very strong in their views that the Israeli occupation of Muslim land is illegitimate and must be dealt with... but that doesn't mean that we are anti-Jew."

On the group's support for al-Qaeda, he said: "The people who form al-Qaeda or the Taleban happen to be Muslims so inevitably every Muslim will have something in common with them.

"We share the testimony of faith, we pray in the same direction, all of us call for Islam, we all support the mujahideen.

"We all believe that issues such as Chechnya and Palestine and Kashmir are Islamic issues, and these are problems which every Muslim feels, and all Muslims want to resolve."

Civil offence

He denied that the group had recruited any young British Muslims to go and fight with the Taleban, as ex-members had previously claimed.

It's not beyond probability that people from our organisation... have gone to one or other of the fronts where the Muslims are fighting jihad

Jim Choudhury

"Our, if you like, methodology involves purely verbal addresses...

"It's not beyond probability that people from our organisation around the world... have gone to one or other of the fronts where the Muslims are fighting jihad.

"But there is a big difference between that and al-Muhajiroun having a policy of recruiting people and training people and engaging in military activities themselves."

Police said by holding the gathering the group was committing a civil offence - but it would be up to the GLA to prosecute those involved.