The government has decided not to order a public inquiry into the murder of Pat Finucane by loyalist paramilitaries in 1989, Northern Ireland secretary Brandon Lewis has said.
The British security services colluded with the Ulster Defence Association in the killing of the Belfast solicitor, who came to public prominence because of his successful human rights legal challenges against the government.
A ruling by the UK Supreme Court in February last year found that there had never been an adequate investigation into the murder, but left it up to the government to decide whether to hold an inquiry.
In 2001 the British government pledged to hold an inquiry under the Weston Park agreement, but one was never set up. The recent Supreme Court ruling acknowledged that this commitment had been an “unequivocal undertaking".
Speaking on Monday afternoon, Mr Lewis told the House of Commons that it was “plain that levels of collusion in the Finuchan case, made clear by previous investigations, are totally unacceptable”.
But he said the court judgment had made it clear that it was “for the state to decide what form of investigation if indeed any is now feasible”.
A separate Police Service of Northern Ireland (PSNI) investigation could yet go ahead, with a Police Ombudsman probe also on the cards.
A 2012 independent review of the death found that British security forces had colluded with the paramilitaries in the killing, and the UK government has accepted this finding.
Mr Finucane, who was 39 at the time of his death, had represented both republican and loyalist paramilitaries during the Troubles.
Irish foreign minister Simon Coveney said ahead of the decision that the British government’s response would indicate whether it was committed to truth and reconciliation.
"If we are to move forward together on this island - both governments, all political parties and indeed most importantly victims and their families - well then we need to see full commitment by both governments to establishing the truth," he added.
Mr Lewis said he acknowledged that “accepting that collusion occurred is not sufficient in itself” and that he would be releasing some new information about the case into the public domain.
But he added: "This government has demonstrated that when the public interest requires it, we will establish public inquiries to look at any potential failings by government or state bodies - as, for example, we've done with the Manchester bombing.
"In this instance, I believe it is in the public interest to allow the police and ombudsman processes to proceed before taking any decision on whether the state's Article 2 obligations have been discharged or whether further steps are required.
"This case, it has to be said, is sadly just one example of the violence and tragedy experienced by so many individuals and families across Northern Ireland, the rest of the United Kingdom and indeed Ireland during the Troubles."
Mr Finucane's widow Geraldine and the couple's three children have been campaigning for decades for a public inquiry to establish the extent of security force involvement.
Pat Finucane's son John said: "We are very angry. What the British government proposed to us today was nothing short of insulting.
"The British government at every opportunity will continue to make the wrong decision and put all their efforts into ensuring that the truth of what happened to my father will not see the light of day and they are intent on suppressing that."
Responding in the House of Commons, shadow secretary of state for Northern Ireland Louise Haigh told MPs: "That this crime could happen at all in our country is shocking, that it has never been investigated to a lawful standard is unjustifiable and we have to ask ourselves, as we do with all legacy issues with the Troubles, do we accept a lesser standard of justice for citizens of Northern Ireland than we would if this terrible crime had happened in our constituencies?"
She added: "It appears that nothing the secretary of state has announced today will make up for these most fundamental shortcomings in previous reviews and the family have described this approach as farcical."