Taoiseach Leo Varadkar has urged Theresa May to do the "honourable thing" and hold a public inquiry into the murder of solicitor Pat Finucane.
The Supreme Court in London ruled this morning that there has been no "effective investigation" into Mr Finucane's murder and that previous inquiries had not complied with the Finucane family's human rights.
Mr Finucane was shot dead in front of his family in February 1989 by loyalists in an attack which an official report later concluded had involved collusion with the UK state.
The 39-year-old was shot 14 times while enjoying Sunday lunch at home with his family.
Mrs Finucane claimed the British government unlawfully "reneged" on a promise to hold a public inquiry into the killing - one of the most notorious of the Troubles - when former prime minister David Cameron instead ordered an independent review by former war crimes lawyer Sir Desmond de Silva QC.
His review concluded that there had been collusion between the killers and the state and Mr Cameron later apologised.
During Leader's Question's today, Taoiseach Leo Varadkar was asked by Sinn Féin leader Mary Lou McDonald whether he would ask his UK counterpart to hold an inquiry to address what she labelled "one of the many broken commitments of the peace process".
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 (@campaignforleo) February 27, 2019
Mr Varadkar hailed the family of Mr Finucane.
"I never had the opportunity to meet Pat Finucane, but I've read about him, I know he was an honourable man, a lawyer and human rights activist - long before people even used that term.
Timeline of Pat Finucane murder probe
"I had the opportunity in recent weeks to meet with Geraldine Finucane and her family," Mr Varadkar said.
"Geraldine made a real impression on me, particularly her dignity and steely resilience seeking justice and truth for three decades now."
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Mr Varadkar said: "The position of the Irish government is that the British government should now honour its commitment to now carry out a public inquiry in accordance with the inquiries act, into the murder of Pat Finucane.
"The British government should keep the promise made by Prime Minister Cameron back in Weston Park in 2001 (Mr Varadkar later corrected the record that this was Tony Blair), and accept the judgment made by the Supreme Court today.
"It is the honourable thing to do, the right thing to do, and I believe the British government should do that.
"I will certainly be raising it in my meetings with the prime minister."
He concluded his answer by stating: "I will be pressing my counterpart Theresa May to honour the commitment made by her forebear."
July 2018: Pat Finucane's family criticise Whitehall for keeping murder files secret
The Supreme Court ruled that the de Silva review was not compliant with Article 2 of the European Convention on Human Rights, which required the investigation to be provided with "the means where, if they can be, suspects are identified and, if possible, brought to account".
But the court also found that, while Mrs Finucane had been given "an unequivocal undertaking" that there would be a public inquiry into the murder, the British government was justified in later deciding against holding one.
