London (CNN) -- A Libyan family has accepted a 2.2 million-pound ($3.5 million) payout to settle a case it brought against the UK government over its role in forcibly returning them to Libya in 2004, the family's law firm said Thursday.
Sami al Saadi, a prominent opponent of former Libyan strongman Moammar Gadhafi, his wife and four young children were bundled onto a plane in Hong Kong as the result of a joint operation by U.S., UK and Libyan intelligence services, legal firm Leigh Day said.
They were then flown to Libya, where all of them were initially imprisoned and Sami al Saadi was held and tortured for a number of years, Leigh Day said.
Documents found at Libyan intelligence headquarters in Tripoli by Human Rights Watch in September 2011 highlighted the cooperation between Libya and Western intelligence agencies after Libya ended its weapons of mass destruction program in 2004.
Among the papers was CIA correspondence with Libyan intelligence found in spy chief Moussa Koussa's office, according to Leigh Day.
It said the CIA correspondence stated: "We are ... aware that your service had been cooperating with the British to effect (Sami al Saadi's) removal to Tripoli ... the Hong Kong Government may be able to coordinate with you to render (Sami al Saadi) and his family into your custody."
The joint operation followed a meeting between then-Prime Minister Tony Blair and Gadhafi in the Libyan desert in 2004, in which a deal was struck on intelligence cooperation, according to Leigh Day and legal action charity Reprieve.
A Foreign Office spokesman told CNN: "We can confirm that the government and the other defendants have reached a settlement with the claimants. There has been no admission of liability and no finding by any court of liability."
He declined to comment further.
"I think the payment speaks for itself," al Saadi said in a statement issued through his lawyers.
He said he had agreed to settle the case because of concerns about moves by the British government to expand the use of "secret courts" in cases involving issues of national security.
"My family suffered enough when they were kidnapped and flown to Gadhafi's Libya. They will now have the chance to complete their education in the new, free Libya. I will be able to afford the medical care I need because of the injuries I suffered in prison," he said.
"I started this process believing that a British trial would get to the truth in my case. But today, with the government trying to push through secret courts, I feel that to proceed is not best for my family. I went through a secret trial once before, in Gadhafi's Libya. In many ways, it was as bad as the torture. It is not an experience I care to repeat.
"Even now, the British government has never given an answer to the simple question: 'Were you involved in the kidnap of me, my wife and my children?' "
Prime Minister David Cameron has defended the government's plans to expand secret hearings under the justice and security bill, saying the measure would allow highly sensitive evidence to be presented that otherwise could not be heard in court.
Al Saadi and his family intend to donate some of the payout to support other Libyan torture victims.
"We look forward to the result of the police investigation and hope there will be a full and fair public inquiry into our case," he added.
London's Metropolitan Police said in January that it would investigate claims that the British secret services were involved in the rendition of al Saadi and a second Libyan, Abdul Hakim Belhaj, to Libya and their alleged ill treatment there.
Belhaj is a former leader of the Libyan Islamic Fighting Group who became a senior revolutionary commander in Libya.
John Sawers, chief of the British foreign intelligence agency MI6, and the Cabinet Office said they would cooperate fully with the police investigation. "The government stands firmly against torture and cruel, inhuman and degrading treatment or punishment," the Cabinet Office said at the time.
Sapna Malik, the lawyer who represented the al Saadi family, said: "The sheer terror experienced by the al Saadi family when they were bundled onto their rendition flight and delivered up to their nemesis clearly lives with them all to this day.
"Having concluded one part of their quest for justice, they now look to the British criminal courts to hold those responsible for their ordeal to account and await the judge-led inquiry they have been promised."
Belhaj said that he respected al Saadi's decision to accept the payout, adding that it was a miracle his friend had survived his imprisonment in Libya.
"I understand and support his decision to provide his family with security, pay for his medical care, and support other victims of torture," he said in a statement issued through Leigh Day.
"I intend to fight to ensure the truth is told. I have said before, and I say again now, my wife and I will not allow the truth to be concealed."
Gadhafi died after he was captured in his hometown of Sirte on October 20, 2011.
CNN's Jo Shelley and Dan Rivers contributed to this report.