Two months ago, when the Canary Wharf bomb went off and signalled the end of the IRA ceasefire, a trigger reflex of new and flexible powers for the police, rushed through parliament, would have been understandable. At times of emergency, of panic even, people expect the ordinary rules that control the introduction of new legislation to be suspended if it is felt that the law needs to be strengthened. Instead, the British government reacted circumspectly, and its main response was to increase the political pressure on Sinn Fein and the IRA to join the negotiating process by changing its stance on decommissioning.

Why, then, did it abruptly decide to use emergency procedures to put extraordinary new powers in the hands of the police? The reason given is that fresh IRA violence was thought to be possible over the Easter weekend to mark the 80th anniversary of the 1916 Rising. This date, however, has not suddenly surged out of the blue. Nor is it credible that the Prevention of Terrorism (Additional Powers) Act, signed into law yesterday afternoon less than 48 hours after it was published, was drafted only in the last few weeks. Its broad sweep suggests contingency planning for a considerable length of time.

Nothing in the way it was presented in the two Houses of Parliament indicates that it is narrowly focussed. The ostensible reason may be an IRA threat, it is intended as a permanent new feature of British law, designed, as a Home Office minister said in the House of Lords, to meet the fact that "terrorism in one form or another will be with us".

To use the emergency procedures of parliament in these circumstances is provocative and also dangerous. The most arbitrary of the new powers - allowing police officers to stop and search anyone at will, after an area has been designated has breathtaking implications: anyone who fails to co operate may be jailed - for up to six months; any infringement of any kind uncovered during such a search may be prosecuted; no effective challenge is possible to a police decision that use of the powers is necessary to investigate "the commission, preparation or instigation of an act of terrorism".

So broad is the scope of the Act, and so deep the threat to minorities and dissidents, that it is difficult to resist the suspicion that it was treated as emergency legislation to minimise any challenge under international human rights conventions. The extent to which the normal parliamentary safeguards were evaded was clear from the complaint of Lord Rodgers, a former Labour minister now in the Liberal Democrats, that members of the Privy Council were not given a confidential briefing on the security threat in order to secure all party backing.

The Act itself is a threat to democracy, but equally serious questions are raised by the failure of the Labour Party to oppose the manner in which it was passed into law. It was left to a minority of MPs to object to the lack of time for debate, and fewer still voted against it. While a consensus against terrorism and political violence is necessary, terrorism succeeds when it manages to impose a limit on democratic probing. That, inevitably, was the effect of Labour's self imposed silence.