Former Foreign Secretary Jack Straw faces being sued by a former Libyan dissident over allegations of abduction and torture.
Abdul-Hakim Belhaj has alleged that MI6 helped the US kidnap him in Asia in 2004 to return him and his wife to Tripoli.
On Tuesday the Supreme Court backed a Court of Appeal ruling allowing his action.
Belhaj was one of the leaders of the uprising against former Libyan leader Colonel Muammar Gaddafi.
He said he was abducted - along with his pregnant wife, Fatima Boudchar - as he was about to fly to London to claim asylum, the BBC reports.
After being returned to Libya, he spent six years in jail. His wife was released shortly before giving birth.
Belhaj has reportedly offered to drop his claim in return for an apology and a token payment of £1 from the British government and its agencies.
Commenting on the Supreme Court’s judgement, Straw said: “This judgment is about some important points of law, related to how far it is possible to bring into a court process in the UK actions of sovereign states abroad.
“However, at no stage so far have the merits of the applicant’s case been tested before any court.
“That can only happen when the trial of the action itself takes place.
“I repeat what I said in the House of Commons in December 2013, that as Foreign Secretary I acted at all times in a manner which was fully consistent with my legal duties, and with national and international law.
“I was never in any way complicit in the unlawful rendition or detention of anyone by other states.”
Martha Spurrier, Director of Liberty, said: “All Mr Belhaj and his wife have asked for, after suffering the most unimaginable abuse, is for those responsible to face up to what they did and apologise.
“Instead, our Government dragged them through years of needless litigation, trying everything in their power to shut them down at every turn.
“It is seven years since David Cameron promised a full judge-led inquiry into our country’s involvement in torture and rendition, and still cover-up and impunity persist.
“Now that President Trump has one foot in the Oval Office, it’s more urgent than ever that our country sends a clear message that there can be no compromise on torture.
“The British public deserve the truth - and torture victims deserve justice.”
Commenting on the decision, Cori Crider, a lawyer from human rights organisation Reprieve, said: “We enter the Trump era with not a soul held to account for Britain’s past role in rendition.
“No official has condemned Trump’s torture boasts. Our intelligence agencies may well be pressured to help America torture again.
“The government bought years of delay by wasting hundreds of thousands of pounds on this appeal, when a simple apology would have closed the case.
“Theresa May should apologise to this family, draw a line in the sand against torture, and restore British honour once and for all.”