The Taoiseach has told the Dáil that a public inquiry must be held into the 1989 killing of Belfast solicitor Pat Finucane.
Pat Finucane, 39, was shot by loyalist paramilitaries in front of his family amid claims of collusion between the killers and security forces.
In February last year, the Supreme Court ruled that investigations into the fatal shooting of the solicitor have not been effective and fell short of international human rights standards.
Micheál Martin said the Oireachtas was of one mind on the need for an inquiry and that would be underlined in a Seanad motion this week.
"I will be engaging with the British Prime Minister on this issue and making it very clear the consistent view of successive Irish governments that there should and must be a public inquiry into the murder of Pat Finucane," he said.
He was responding to a question from Sinn Féin leader Mary Lou McDonald, who said that only a public inquiry would assist the Finucane family in getting the truth.
It was agreed between the British and Irish governments in Weston Park talks in 2001 that an inquiry should be held.
Mr Martin said that where sovereign governments entered into an agreement, it should be adhered to and he said he was asking the British government to do the right thing.
Northern Ireland Secretary Brandon Lewis is deciding whether to order an inquiry by the end of November.
The Taoiseach said he met Mr Finucane's widow Geraldine and son John yesterday.
"There must be a full public inquiry into the murder of Pat Finucane"@MichealMartinTD says he will be engaging with the British Prime Minister and making it "very clear" that there should and must be a full inquiry into the murder of Pat Finucane| More: https://t.co/2pPZIie9ys pic.twitter.com/4Kv6rUo5Zk— RTÉ News (@rtenews) November 24, 2020
He said he made it very clear to them that they would have the "full weight of the Taoiseach's office behind their endeavour".
"For more than 30 years Geraldine and her family have campaigned tirelessly to get to the truth of what happened to Pat," he said.
"It's been a very long journey and they have conducted it with great dignity and determination.
"The Irish Government has walked with them on that journey and will continue to do so until the commitments entered into at Weston Park are honoured."
He added: "We will engage with the British Prime Minister and given the extraordinary perseverance of the Finucane family, in my view, it is more than timely for the British government to respond appropriately in establishing a full public inquiry."
Additional reporting PA