Proposed new anti-terror laws could give police greater powers to stop and question anyone in the UK.
The proposal, allowing police to ask people about their identity and movement, is among measures being considered by Home Secretary John Reid.
The new legislation would be similar to that already used in Northern Ireland.
Police are still likely to need a “reasonable suspicion” a crime may be committed. Anyone refusing to co-operate could be fined up to £5,000.
At present, under section 44 of the Terrorism Act 2000, officers already have the power to stop and search people or vehicles in an area seen as being at risk from terrorism even if they are not suspected of any breach of the law.
A Home Office spokeswoman said that the new proposals would give officers an automatic right to stop and question anyone in the UK about suspected terrorism.
Critics including civil liberties campaigners, Muslim groups, opposition parties and Northern Ireland Secretary Peter Hain expressed their concerns about the effectiveness of the proposals.
Peter Hain, the Northern Ireland Secretary, warned that Britain must take care that its anti-terror legislation does not alienate whole communities, such as Muslims.