The Prevention of Terrorism Acts were a series of Acts of Parliament in the United Kingdom from 1974, which conferred emergency powers upon police forces where they suspected terrorism.

In 2000 it was repealed and replaced with the more permanent Terrorism Act 2000.

The Prevention of Terrorism (Temporary Provisions) Act 1989 had seven parts:

  • Proscribed Organisations allowed for organisations to be made illegal, making membership an arrestable offence. It was also an offence to soliciting financial support for any listed group, display signs of public support, or attend a meeting supporting a listed group or addressed by a group member. The maximum penalty was ten years imprisonment and an unlimited fine. The intial groups outlawed were the IRA and the INLA in the United Kingdom and numerous Loyalist groups within Northern Ireland.

  • Exclusion Orders could be issued "as expedient" to prevent terrorism relating to Northern Ireland. Orders were issued against individuals to either prevent them entering or being in Great Britain, to exclude them from Northern Ireland, or to exclude them from the United Kingdom. It was an offence to breach an order or to aid another in effecting entry, the maximum sentence was five years imprisonment and an unlimited fine.

  • Financial Assistance for Terrorism. As well as the provision under the first part of the Act, contributing, receiving or soliciting financial support for terrorism was an offence under this part also. Additionally it was an offence to contribute any other resources; to assist in the retention or control of funds for proscribed groups or terrorist acts; or to fail to disclose to the police any suspicions notwithstanding any other restriction. The maximum penalty was fourteen years imprisonment and an unlimited fine.

  • Arrest, Detention and Control of Entry. This part allowed for the arrest of individuals without a warrant and on reasonable suspicion that they were guilty of an offence under the act or otherwise "concerned in the commission, preparation or instigation of acts of terrorism." The period of inital detention was up to 48 hours, this could be extended to a maximum of five days by the Home Secretary. The detainee was exempted from certain provisions of other acts relating to the arrest procedure and the legal protection of those arrested. This part also allowed for streamlined search procedures of persons or property and checks under the act on persons at port or other border controls.

The remaining parts of the act (Information, Proceedings and Interpretation, Further Provisions for Northern Ireland, and Supplementary) are largely technical although the Northern Ireland provions extends the right to search property, restricts remission for those convicted of statutory offences, and tightens control over the granting of licenses under the Explosives Act 1875 (new explosives factories and magazines).

The first Act was enacted in 1974 following the IRA bombing campaigns of the early 1970s. The act was introduced by Roy Jenkins, then Home Secretary, as a severe and emergency reaction to the IRA threat. It passed into law without substansive debate.

It was rewritten in 1978, 1984 and again in 1989, but continued to stay as emergency 'temporary' powers, that had to be renewed each year. The first three acts all contained final date clauses beyond the annual renwal, this provision was not included in the 1989 act. The inclusion of the "Temporary Provisions" statement in the act is somewhat disingenuous, much of the initial act's legislation has passed into permanent law and the annual renewal of the act was never a threat to its existence.

The exclusion orders were used by the British government to ban prominent Sinn Fein MPs like Gerry Adams to enter Great Britain, and was later held to ban the broadcast of their voices on television and radio.