Victims' families, human rights organisations and all major political parties on the island of Ireland - both Irish nationalist and British unionist - have condemned the law as a denial of justice. The Irish government has said it is considering mounting a legal challenge.
"We cannot give an amnesty to killers. That is not justice," said Eugene Reavey, whose three brothers were murdered by pro-British militants in 1976 but no one has been prosecuted. He described the passage through parliament as "unbelievably bad news" and a "despicable" development.
Around 3,600 people died in three decades of confrontation between Irish nationalist militants seeking a united Ireland, pro-British "loyalist" paramilitaries and the British military. The conflict largely ended with a 1998 peace deal.
Britain argues that prosecutions linked to the events of up to 55 years ago are increasingly unlikely to lead to convictions and that the legislation is needed to draw a line under the conflict.
The bill would create a new Independent Commission for Reconciliation and Information Recovery, which would offer immunity to anyone who cooperates with investigations.
It would prevent full inquests, criminal prosecutions or civil claims into related crimes from the "Troubles" period, but would not impact individuals who have already been convicted, or if a prosecution has already begun.
The House of Commons voted on Wednesday to overturn amendments made to the bill in the upper chamber, the House of Lords, meaning the bill just requires Royal Assent, where it is formally approved by the King, to become law.
Amnesty International described the passage as a "dark day" for justice in the country.
Ireland's government has said it would consider taking a legal challenge against the law for violating the European Convention on Human Rights. The British government has said the law is fully compliant.
Hilary Benn, Northern Ireland spokesperson for the opposition Labour Party, told a debate in parliament that a Labour government would repeal the bill.
