A former leader of the Libyan Islamic Fighting Group [LIFG] is taking legal action against ex-foreign secretary Jack Straw in what is thought to be the first case of its kind against a senior ex-minister.
Abdel Hakin Belhadj, 45, accused Straw of signing the papers approving his rendition and is seeking compensation.
The amount claimed was unclear but Belhadj's lawyers said they were not ruling anything out.
Sapna Malik, a partner of law firm Leigh Day & Co, said that liability must "follow the chain of command".
She said: "The civil action is against Mr Straw personally and seeks his response to allegations that he was complicit in torture and misfeasance in public office.
"If the former foreign secretary does not now own up to his role in this extraordinary affair, he will need to face the prospect of trying to defend his position in court."
If the claim comes to court Straw may face a tough legal battle and, ultimately, criminal charges.
Malik told BBC Radio 4's Today: "The real issue is not about the amount of compensation, it's really to get public acknowledgement and an admission from Jack Straw and those others involved in their role in his rendition.
"It's not some sort of cheap publicity stunt. There are real concerns about who signed off on what."
Belhadj claims that in 2004 the CIA took him against his will from Thailand to Libya via Diego Garcia in the Indian Ocean.
As an opponent of the anti-Gadaffi regime, Belhadj was living in exile in Beijing and he and his wife were on their way to Britain to claim political asylum when they were abducted.
They were allegedly tortured throughout the rendition process and subsequently imprisoned in Libya, the country he had sought asylum from.
MI5 officers had previously thought that Belhadj and the LIFG had close links with al-Qaeda.
Papers have already been served to the high court allow him to sue the UK government, UK security forces and MI6 officer Mark Allen for damages.
Straw is on record in a BBC interview as saying that the Labour government, with whom he was foreign secretary from 2001-06, was against rendition.
"We were opposed to any use of torture or similar methods," he said. "Not only did we not agree with it, we were not complicit in it and nor did we turn a blind eye to it.
But he added: "No foreign secretary can know all the details of what its intelligence agencies are doing at any one time."