The judge, Mr Justice Colton, said he was satisfied the provisions of the act that offer immunity from Troubles-era prosecutions breached Articles 2 and 3 of the European Convention on Human Rights.

The judged said there was "no evidence that granting immunity under the Act would in any way contribute to reconciliation in Northern Ireland", adding the "evidence is to the contrary".

However, the judge also ruled that new Independent Commission for Reconciliation and Information Recovery (ICRIR) set up by the act was capable of making effective investigations and was not in breach of human rights law.

Mr Justice Colton told Belfast High Court: "I fully understand the opposition to the new scheme and the reasons for it.

"That said, I cannot at this remove say the system established under the Act cannot provide an Article 2 and 3 compliant investigation.

"It has wide powers and wide range of discretion to carry out its reviews. Should it fall short of its obligations on Articles 2 and 3, I have no doubt they will be subject to the scrutiny of the court."

A legal challenge was mounted by a number of victims' relatives against the act, which aims to end Troubles-related prosecutions and brings in a conditional amnesty for suspects, provided they cooperate with the ICRIR.

Four people had challenged the human rights compliance of the act, including its denial of inquests, lack of adequate investigations and ban on civil proceedings.

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Martina Dillon's 45-year-old husband Seamus was shot dead in a loyalist gun attack at the Glengannon Hotel in Dungannon, Co Tyrone, in 1997.

John McEvoy survived another loyalist gun attack in Kilcoo, Co Down, in 1992, in which another man died.

Lynda McManus's father James was injured in the notorious Sean Graham bookies massacre, also in 1992. That was carried out by the loyalist UDA group.

Brigid Hughes lost her husband Anthony, an innocent civilian who was killed by the SAS as they shot dead eight IRA members in Loughgall in 1987.

Lawyers expect appeals in the case, which could be brought all the way to the Supreme Court and could take several years to exhaust.

In December, Ireland announced it was taking legal action against the UK in the European Court of Human Rights, for only the second time in 50 years.

The Irish government said it had received legal advice that the new UK law was in breach of international human rights legislation, and the move was being taken "with regret".

It has severely strained Anglo-Irish diplomatic relations, which may improve if a Labour government is elected at the next election. Party leader Keir Starmer has vowed to repeal the controversial legislation.