The British government has decided not to hold a public inquiry into the murder of Belfast solicitor Pat Finucane.
Britain's Northern Ireland Secretary of State Brandon Lewis, speaking in Westminster, said he had told the family of the decision not to hold an inquiry at this time.
The Finucane family said the decision was "astonishing, arrogant and cruel".
They promised to continue campaigning until their questions were answered.
The British Supreme Court, in February 2019, ruled that the UK had failed to hold an "effective investigation" into the Belfast lawyer's death at the hands of loyalist paramilitaries.
It was up to the state to decide what action to take on the back of this ruling, Mr Lewis said. The British government had decided not to opt for a public inquiry.
Mr Lewis told MPs he is "not taking the possibility of a public inquiry off the table at this stage", adding the PSNI and police ombudsman processes must move forward without the risk of prejudicing any emerging conclusions from their work.
Mr Lewis went on to explain how a number of issues were referred to the police ombudsman in 2016, noting: "In addition, the legacy investigation branch of the PSNI informed my department on 2 November 2020 that Patrick Finucane's case is shortly due to undergo a process of review in accordance with the priorities set out in their case sequencing model.
"The chief constable confirmed this is expected to begin early in the new year. To be clear, this is a purely operational police matter. The UK Government, rightly, has no role whatsoever in determining how or when the police deal with their outstanding legacy caseload.
"However, the fact a decision on a police review is due shortly is an important development and was a factor in determining the next steps in this case. Critically, a review would consider whether further investigative steps could be taken in this case and whether the PSNI should do so."
Mr Finucane, a 39-year-old solicitor who represented both republican and loyalist paramilitaries during the Troubles, was shot dead in his family home in north Belfast in February 1989 by the Ulster Defence Association in an attack found to have involved collusion with the state.
His widow Geraldine and their three children have been campaigning for decades for a public inquiry to establish the extent of security force involvement.
Taoiseach Micheál Martin said he was disappointed that the British government has not committed to holding a public inquiry, as agreed between the British and Irish governments in 2001.
PSNI Chief Constable Simon Byrne, in a statement, said the statutory duty for investigating deaths during the Troubles continues to sit with the Police Service of Northern Ireland.
Describing the murder of Mr Finucane as a "truly horrendous crime", he said it is "our view that there are currently no new lines of inquiry. We now need to decide if a further review is merited given all the previous investigations into this case.
"Once we have determined that, we will inform the Finucane Family. If we determine that a review should take place, we will then have to decide if we are best placed to carry out that review."
Chief Constable Byrne added: "As it stands it is unlikely that we would enjoy a perception of independence in this case, given the accepted position of State involvement in this matter. Therefore, it is highly likely that any review would need to be conducted independently."
Earlier Sinn Féin warned that a failure to order a public inquiry into the murder would have profound implications for confidence in the rule of the law.
Speaking before Britain announced its decision, Sinn Féin vice president and Stormont Deputy First Minister Michelle O'Neill said it was a "day of reckoning" for the Finucane family.
She said: "The British government's approach of delay and denial has literally run out of road."
Last year, Britain's Supreme Court said all previous examinations of the death had not been compliant with human rights standards.
The court acknowledged Ms Finucane had been given an "unequivocal undertaking" by the UK government following the 2001 Weston Park agreement that there would be a public inquiry into the murder.
However, the Supreme Court judges found that the UK government had been justified in later deciding against holding one.
The court said it was up to the UK government to decide what form of investigation was now required, if one was feasible.
Amid a government delay in responding to the judgment, Ms Finucane took fresh judicial review proceedings against the state.
Last month, the UK's Northern Ireland Secretary of State Brandon Lewis's lawyers gave a High Court judge in Belfast a commitment that a decision would be announced by Monday 30 November.
Ahead of that conversation, Ms O'Neill said: "It is a matter of huge public interest that there is full and maximum disclosure around questions about who ordered the killing, about who knew what, and when.
"Those involved must be held accountable. Until now there has been virtual impunity for the British state agencies and actors involved in the killing.
"Any attempt by the British government to ignore the family, political and wider public demands for a public inquiry will have profound and fundamental implications for confidence in the rule of law, the administration of justice and the wider approach to legacy.
"Now is time for the British government, and the British Secretary of State Brandon Lewis, to finally listen to the Finucane family and call a public inquiry as a matter of public interest. There can be no further delay."
Former UK prime minister David Cameron decided not to hold a public inquiry into the murder, but instead ordered a review of all the files related to the case by former UN war crimes prosecutor Desmond de Silva.
Mr de Silva Desmond found significant levels of state collusion involving the army, police and MI5, but said there was no evidence of an "overarching state conspiracy".
His findings prompted Mr Cameron to apologise to the Finucane family for "shocking levels of collusion".
However, Mrs Finucane branded the de Silva report a "whitewash".
Last week, three other Stormont parties, the SDLP, Alliance and Greens, joined Sinn Féin in writing to Mr Lewis to demand a public inquiry.
The Government also called on its UK counterparts to order a probe, as did 24 members of the US Congress.