The Home Secretary today described the implementation of further tough measures from the Nationality, Immigration and Asylum Act as the 'most overarching and radical reform' of citizenship and immigration laws for 30 years.

From today UK citizenship can be removed from people with dual nationality who act in a way that is 'seriously prejudicial' to the UK's interests, or from people who obtained citizenship by deception.

It is one of the most controversial measures in the legislation, and it has been widely speculated that the Government might target people such as Abu Hamza, the controversial Muslim cleric who has dual nationality and was recently banned from preaching at the Finsbury Park Mosque because of his political comments.

However, the NIA Act has caused concern among civil liberties groups with the director of Liberty, John Wadham, commenting today: 'Any decision to strip someone of citizenship should be for a court, based on evidence of treason or similarly serious offences.'

'Politicians are too easily drawn into action by popular witch-hunts or the jibes of political opponents - citizenship is something that shouldn't be given or taken away that lightly.'

And Keith Best, director of the Immigration Advisory Service, told the BBC ahead of the implementation of the laws that if someone had done something wrong they should be charged with a criminal offence not deported.

He added: 'These are very wide powers for the Secretary of State. There is no guarantee that the individual will ever see the evidence.'

Overall, more than two-thirds of measures in the NIA Act are now in place to prevent abuse of the asylum system, which include:

* allowing claimants to be sent back to 'safe' European countries without the ability to appeal
* a new five-day limit for detainees to lodge appeals
* and the prevention of multiple appeals on grounds that could and should have been raised at an earlier stage.

As well as measures to stop illegal working, others include:

* giving immigration officers' powers to enter and search business premises
* making it simpler to prosecute those guilty of employing illegal workers
* and a new power for the Inland Revenue to disclose information to the Home Office to identify illegal workers and remove them from the UK.

David Blunkett commented: 'When I published the White Paper which set out our plan, I said that obtaining and holding British citizenship should be a meaningful event and one which is respected as something that carries with it rights and responsibilities.'

He added that if the UK was to welcome those who aspire to British citizenship it also had to clamp down on those whose aims are 'totally incompatible with holding British citizenship.'

Mr. Blunkett went on to express his hope that the 'encouraging reductions' in the number of asylum applications that were reported last would continue with the implementation of the NIA Act.

Earlier this year the Prime Minister pledged in a television interview that the number of asylum applicants to the UK would be halved by September.

Figures for 2002 show that for the first time the number of asylum applications went over the 100,000 mark.

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