There have been fresh demands for the UK Government to launch a full, frank and fair investigation into allegations it sanctioned the torture of some internees during the Troubles.
The calls, led by Amnesty International, come after the Irish Government referred the case of the so-called Hooded Men to the European court earlier this week.
Patrick Corrigan, Amnesty's programme director for Northern Ireland, said there was an obligation to hold those responsible to account.
He said: "It is utterly unacceptable that, in 43 years, the UK authorities have never conducted a proper investigation into the abuse and that no-one, not the people who carried out the abuse, nor the people who authorised it, has ever been held accountable before the law."
The case centres on 14 Catholic men who were interned - detained indefinitely without trial - in 1971 who said they were subjected to torture methods including hooding, being held in stress positions, exposure to white noise, sleep and food deprivation as well as beatings.
The men were hooded and flown by helicopter to a secret location, later revealed as a British Army camp at Ballykelly, outside Londonderry.
They were also dangled out of the helicopter and told they were high in the air, although they were close to the ground.
None were ever convicted of wrongdoing.
Paddy Joe McClean, a father of 12 from Beragh in Co Tyrone and former chairman of the Northern Ireland Civil Rights Association, said he hoped for an official apology for the brutal treatment to which he and others were subjected.
Mr McClean said: "We were taken to some unknown destination and were put through all the different forms that have been noted - wall standing, hooding, being beaten about the legs and arms and all that. That happened for four days.
"It was horrific because we were kept hooded for that length of time and you were not given anything to eat. You actually didn't know what was going to happen and you assumed that nobody could let you out to tell about it. It wasn't what you would expect in a civilised society.
"An apology from the Prime Minister would do. Whether he's speaking in Parliament or outside of it, it doesn't matter as long as he makes the statement.
"But, he'd be worried about the implications of it and I understand that."
Mr McClean was among 10 of the Hooded Men who gathered at Belfast's Stormont Hotel for a private meeting with Thomas Hammarberg, who investigated internment abuses for Amnesty International in 1971.
The others were Francie McGuigan, Kevin Hannaway, Liam Shannon, Jim Auld, Joe Clarke, Gerry McKerr, Michael Donnelly, Patrick McNally and Brian Turley.
Relatives of some who have since died were also in attendance.
Mr Hammarberg said: "Time does not heal all wounds, if justice is not done.
"Now that an application has been made by Ireland to revisit the judgment, it should be in the interest of the UK government, as a signatory of the UN Convention against Torture and the European Convention on Human Rights, to ensure that the facts be clarified in this critical case and remedial action be taken."
The Irish government first took a human rights case against Britain over the alleged torture in 1971.
The European Commission ruled that the mistreatment of the men was torture, but in 1978 the European Court of Human Rights held that the men suffered inhumane and degrading treatment that was not torture.
The UK did not dispute the finding.
New evidence, uncovered from national archives in London, has thrown doubt over the ruling. It includes a letter dated 1977 from then-home secretary Merlyn Rees to then-prime minister James Callaghan in which he states his view that the decision to use "methods of torture in Northern Ireland in 1971/72 was taken by ministers - in particular Lord Carrington, then secretary of state for defence".
The Irish government had until December 4 - six months after the new evidence came to light - to inform Europe if it wanted the case reopened.
A High Court case was launched in Dublin seeking to compel the Cabinet into acting.
Amnesty International said reopening the case would help the surviving Hooded Men and the families of those who have died to their right to truth and justice
Mr Corrigan added: "The allegations against the UK are extremely grave: that they tortured their own citizens, knowing full well the long-term effects of the abuse, that this was authorised at the highest levels of government, and that they then deliberately misled the European Court of Human Rights.
"The Irish government has done the right thing by referring this case back to the European Court. The spotlight now falls on the UK and its obligation to deliver an independent and effective investigation into the allegations."