Sinn Féin leader Mary Lou McDonald has said the Taoiseach must push for a public inquiry into the murder of Belfast solicitor Pat Finucane during his meeting the British Prime Minister Keir Starmer.
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 1989 by the Ulster Defence Association in an attack found to have involved collusion with the British 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.
In 2020, the British government decided it would not hold a public inquiry into the murder.
The decision came in the wake of a British Supreme Court ruling, in February 2019, that the UK had failed to hold an "effective investigation" into the Belfast lawyer's death.
Ms McDonald said she wrote to Simon Harris urging him to raise the matter with Mr Starmer when they meet in London.
"The case for a public inquiry to be held which is long overdue and decision time draws near," she said.
"In 2019, the Supreme Court in London declared that previous investigations commissioned by successive British governments into the murder of Pat Finucane by loyalists to have failed to meet the standards required by Article 2 of the European Convention on Human Rights.
Ms McDonald added: "For decades now, Geraldine Finucane and her family have led a dignified campaign for truth and justice, seeking a public inquiry into her late husband's murder.
"They have rightly received strong support from Sinn Féin and the Irish Government in this regard.
"In the latest case last week, the Court of Appeal set out a timetable for action, requiring the British government to respond within three weeks and agree to an Article 2 compliant investigation into Pat Finucane’s murder," she said.
Writing then when she was UK Shadow Secretary of State, Louise Haigh said it was "shocking" that "this crime could happen at all in our country".
"That it has never been investigated to a lawful standard is unjustifiable," she wrote.
"It is my view, and the long-standing view of the Labour Party inside and outside of government, that an independent public inquiry is the only remaining mechanism which can establish the full truth and deliver on promises made to the family."
Mr Harris will travel to the UK later to meet Mr Starmer. It is expected that the pair will discuss ways to improve Anglo-Irish relations.