Islamic extremists boasted of how they would never be thrown out of Britain yesterday as a promised crackdown by the Government turned into a shambles.

The hardliners taunted Home Secretary Charles Clarke after he promised action 'within days' to start deporting dozens of foreign preachers of hate living in the UK.

Headed by asylum seeker Yasser Al-Siri, who is suspected of involvement in a series of terrorist incidents, they gloated that lawyers would halt any attempt at their removal.

The Egyptian, who fled to London more than a decade ago and is wanted in the U.S., said: 'I am not worried about expulsion. My legal team think it is impossible.'

Al-Siri's defiance came as Mr Clarke's plans were attacked by leading lawyers and moderate Muslims. They warned the deportations policy would breach international law, create massive confusion and turn Muslims against the Government.

Tony Blair first pledged tough action to remove hate preachers on August 5 before heading away on his summer break. Yesterday

Mr Clarke confirmed the wide-ranging list of 'unacceptable behaviours' which he said could lead to extremists being thrown out of the country or barred from entering in the first place.

It ranges from the expression of views which 'foment, justify or glorify' terrorism to those which 'foster hatred which might lead to intercommunity violence'.

Mr Clarke said the measures were necessary to counter the 'real and significant' terrorist threat facing the country after the suicide bombings in London on July 7.

But legal experts said that, under human rights laws, he could not send anybody back to countries where they could face torture or death.

Britain is trying to secure 'memorandums of understanding' with North African and Middle Eastern countries to overcome this hurdle, but so far has only managed an agreement with Jordan.

The Government has also signalled it is prepared to amend the Human Rights Act to achieve its aims.

But Al-Siri, who faces execution in Egypt for the murder of a six-year-old girl in a terror bomb blast, said: 'I don't think any British judge can accept any agreement between the UK and any Middle East country like Egypt.'

The 42-year-old, who denies involvement in terrorism, added: 'Any judge here can take this agreement and throw it in the rubbish basket.

'I still trust the UK with human rights and, while Tony Blair may want to change the laws, there is still the Magna Carta.'

Saudi dissident Dr Saad Al-Fagih, who has been described as 'global terrorist' by the U.S., also said he was not worried by Mr Clarke's threat.

He said: 'There is no reason why I should go, none whatsoever. I am doing nothing wrong. If any attempts are made I will contact my lawyer and go through the due process.'

Al-Fagih, who lives with his wife and four children in a £600,000 semi in Willesden Green, North-West London, added: 'If the legal process is transparent I have no need to worry.'

Home Office insiders said Mr Clarke planned to take action against 'dozens' of extremists. The process will start within days, according to the bullish Home Secretary.

Those who could be targeted include Al-Siri, Al-Fagih and fellow Saudi Mohammed Al-Masari, a leading supporter of Osama Bin Laden who has said it would be legitimate for Muslims to assassinate the Prime Minister.

But human rights group Liberty said it was convinced the memorandums would not satisfy international human rights law.

The deportations are likely to be tested in the Court of Appeal, House of Lords and, ultimately, the European Court of Human Rights in Strasbourg in a process lasting up to three years.

Ten extremists rounded up by officials ten days ago have already lodged appeals.

Liberty's legal director James Welch said: 'What has always separated us from the terrorists is that we do not torture people or send them to be tortured - that is the standard we need to maintain.'

Mr Clarke's definitions of ' unacceptable behaviour' also came under attack, amid predictions they too would face legal challenges.

Ian Macdonald QC, who resigned his post on the special immigration appeal court last year over the Government's anti-terror laws, said the new criteria neither added to the Home Secretary's powers nor made things clearer.

He said the descriptions appeared to have been drawn up 'on the back of an envelope'.

Asghar Bukhari, of the Muslim Public Affairs Committee, said the Government risked turning the Muslim community against it if people were no longer allowed to speak out on issues such as Palestinian rights.

The Nationalist Alliance says: Just deport them - what 'Human Rights' did their victims have?