Mr Finucane, a Belfast solicitor, was shot and killed by loyalist paramilitaries in collusion with the UK security forces in 1989.

Last February, the UK Supreme Court ruled that investigations into the shotting of the 39-year-old did not meet international human rights standards.

Louise Haigh, the shadow secretary of state for Northern Ireland, has pledged her support to the Finucane family. She has written to Prime Minister Boris Johnson, calling on him to establish a public inquiry.

“That this crime could happen at all in our country is shocking; that it has never been investigated to a lawful standard is unjustifiable,” she wrote.

“The delay by the secretary of state [in reaching a decision on complying with the law] has added insult to injury.”

She added: “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.

“The long years which have passed since the ceasefire and the Good Friday Agreement have served to demonstrate that, unless justice is done, and seen to be done, the wounds of the past simply will not be allowed to heal. I therefore urge you to act without delay.”

Mr Finucane was shot 14 times in front of his wife and children by gunmen from the Ulster Defence Association.

Three weeks prior to the killing, Douglas Hogg, then a Conservative MP, had said in the Commons that a number of lawyers in Northern Ireland were “unduly sympathetic to the IRA”.

A review in 2012 undertaken by Sir Desmond de Silva QC found there was “no overarching state conspiracy” but that there were “shocking” degrees of state collusion that involved the police, army and MI5.