The Taoiseach Leo Varadkar has said there should be an independent public inquiry into the murder of Belfast solicitor Pat Finucane.
His comments came after Mr Finucane's family lost a UK Supreme Court challenge over the decision not to hold a public inquiry into his murder.
However, they won a declaration that an effective investigation into his death was not carried out.
The court unanimously found that there has not been an investigation compliant with Article 2 of the European Convention on Human Rights.
Following the ruling, Mr Finucane's son John said: "It is time for the murder of Pat Finucane to be properly and publicly investigated in a public inquiry."
We have won!
The British Govt. now knows that it cannot conceal the truth any longer. Today they have been told this by the highest court in the land.
It is time for the murder of Pat Finucane to be properly & publicly investigated in a public inquiry.
Nothing less will suffice— John Finucane MP (@johnfinucane) February 27, 2019
Mr Finucane represented IRA hunger strikers and was killed in front of his family by Ulster Defence Association (UDA) gunmen at his home in February 1989.
The Finucane family had claimed that former British Prime Minister David Cameron reneged on a commitment, given to their family, for a public inquiry into the circumstances of his murder.
Geraldine Finucane appealed against a 2015 judicial ruling that the decision taken by Mr Cameron in 2011 was lawful.
A report carried out by barrister Desmond da Silva in 2012 found that employees of the British State and State agents played a key role in his murder.
The report found there was no "over-arching State conspiracy to murder Patrick Finucane".
But Mr da Silva said: "I am left in significant doubt as to whether Patrick Finucane would have been murdered by the UDA in February 1989 had it not been for the different strands of involvement by elements of the State".
He added: "I believe that it is likely that an RUC officer or officers did propose Patrick Finucane, along with at least one other individual... as a target".
In its judgement on Wednesday, Britain's Supreme Court said: "The Supreme Court holds that Mrs Finucane did have a legitimate expectation that there would be a public inquiry into Mr Finucane's death, but that Mrs Finucane has not shown that the government's decision not to fulfil this promise was made in bad faith or that it was not based on genuine policy grounds.
"The Supreme Court makes a declaration that there has not been an Article 2 compliant inquiry into the death of Mr Finucane".
Mrs Finucane spoke after the ruling in London.
"This is a historic moment. I stand before you today outside the United Kingdom Supreme Court with one simple message: we won.
"The British government now knows that it cannot conceal the truth any longer.
"They have now been told this by the highest court in the land.
"It is time for the murder of Pat Finucane to be properly and publicly investigated in a public inquiry. Nothing less will suffice."
In a statement after the judgement, Mr Varadkar said: "The Finucane family and the British government will wish to consider this judgment in full.
"The Government will also be examining the judgment closely."
"The Government's position is that an independent public inquiry into the murder of Pat Finucane should be established, in line with the political commitments made by the British and Irish Governments at Weston Park in 2001.
"The Government has made this position consistently clear to the British government, and will continue to do so.
"I have met with the Finucane family in recent months, as has the Tánaiste, to confirm the Government's ongoing support for their search for truth and justice.
"The Department of Foreign Affairs and Trade is in ongoing contact with the family at this time."
In the light of the judgment in the UK Supreme Court and the British Government’s political commitments made in 2001, a Public Inquiry into the murder of Pat Finucane must be established
— Leo Varadkar (@LeoVaradkar) February 27, 2019
