From 19th February, there are hundreds, perhaps even thousands more "terrorist suspects" in Britain. Under the new Terrorism Act protestors and activists, with no interest in overthrowing the state or harming the general public, could find themselves falling under the Act's expanded definition of terrorism.

These people could find themselves subject to draconian powers of investigation and incommunicado detention (up to seven days) - even though, as the experience of previous terrorism laws has proven, the vast majority will never be charged with a remotely terrorist offence.

The Act's extended definition of terrorism includes the use or threat of action that involves serious damage to property (eg GM crops?); is designed to interfere with an electronic system (hackers beware); or "creates a serious risk to the health or safety of the public or a section of the public". The definition is so wide and vague that much will depend on the police's interpretation as to who is a terrorist. In fact the police already have very substantial powers under existing criminal law (which already covers most of the offences this Act seeks to address).

The Act creates a two-tier system - in which people suspected of a criminal act for moral or political reasons will have less rights than someone who commits a similar crime for reasons of lust, greed or viciousness. We believe that the public, like us, may have difficulty in understanding that GM food protestors or anti-roads protesters as 'terrorists' in the accepted meaning of the word.

The Home Secretary now also has the right to ban a whole range of groups. Liberty believes that only actions should be subject to criminal sanctions and imprisonment, not mere indications of support or involvement in political organisations: freedom of expression and assembly are too important in any democratic society to be eroded in this way. Furthermore this particular law is unnecessary: under the general law it is already a criminal offence to aid and abet another to commit an offence, so direct support and raising money for the purposes of crime are already outlawed.

Under this Act, exiled supporters of Nelson Mandela who publicly supported the armed struggle in South Africa would have been classified as terrorists. The offence of "incitement" may be committed by mere words and there will be clashes with the right to freedom of expression. Investigation of such offences will often be brought about by political forces such as overseas governments complaining about the tactics of pressure groups and government opponents based in this country.

To enforce the new offences, the British authorities will have to rely on the co-operation and integrity of overseas governments and agencies without proper safeguards. The UK could become tainted by the practice and conduct of investigative bodies overseas which fall far short of our own standards. It will also be very difficult to ensure that the trials are fair if the witnesses and evidence are from another country.

Those who support struggles for human rights and democracy in other countries may find themselves under investigation by the police. Those who have fled from repressive regimes to the safety of this country will become a legitimate target of the police merely because they support the overthrow of that regime, even when they themselves are opposed to violence.

We are also particularly concerned by the duty under Section 19 to disclose any knowledge of terrorist activities (such as fundraising) to the police as soon as possible, along with the information on which this belief or suspicion is based. We believe this may create problems for investigative journalists wishing to protect the identity of their sources.