An intelligence sharing regime between British and US security services was unlawful, a surveillance watchdog has ruled.

The Investigatory Powers Tribunal (IPT), which deals with complaints against GCHQ, MI5 and MI6, found that intercepted communications were provided to Britain’s listening post GCHQ in breach of human rights laws.

However, during the proceedings leading up to the judgment, the government revealed details of the legal framework governing the bulk interception and intelligence sharing regime — and by doing so had now made it compliant with the European Convention on Human Rights, the IPT said.

The ruling effectively means that the intelligence sharing programme was unlawful until December because the public were unaware of the safeguards in place — but since they were revealed by the hearings the human rights violation has been addressed.

It is the first time the IPT has found against the intelligence agencies in its 15-year history.

Human rights groups Liberty, Privacy International and Amnesty argued that GCHQ’s methods breached Article 8 of the European Convention on Human Rights (ECHR), the right to privacy, as well as Article 10, which protects freedom of expression.

Yesterday’s ruling was broadly welcomed by the groups, however, they dispute the claim that the safeguards are sufficient to make GCHQ’s intelligence-sharing activities lawful.

James Welch, legal director for Liberty, said: “We now know that, by keeping the public in the dark about their secret dealings with the National Security Agency, GCHQ acted unlawfully and violated our rights.”