The government spent more than £11m of public funds resisting demands for an apology, compensation and prosecutions over MI6’s 2004 rendition of the Libyan dissident Abdel Hakim Belhaj and his wife, Fatima Boudchar.

The colossal sum involved has been revealed for the first time through a freedom of information request that exposes the vast amounts ministers and official were prepared to pay out at a time when legal aid has been severely restricted.

In the end – following eight years of sprawling, legal actions that reached the supreme court – Theresa May offered an unprecedented apology in parliament to the couple for the mistreatment they endured.

Lawyers for the government were paid £4.4m while those acting for Belhaj and Boudchar received £6.9m. Both figures came out of government funds.

Belhaj and Boudchar were seized in Thailand by CIA officers in 2004 before being hooded, shackled and flown to one of Muammar Gaddafi’s prisons, where Belhaj was tortured and sentenced to death. He was released six years later. Boudchar was four and a half months pregnant when she was abducted. She was released shortly before giving birth.

Internal Libyan security documents that surfaced after the revolution in Tripoli revealed the role played by British intelligence officers in their kidnapping. Boudchar eventually received £500,000 compensation; her husband wanted only a public apology.

Fatima Boudchar and her son, Abderrahim Belhaj. Photograph: Christian Sinibaldi/The Guardian

The Government Legal Department (GLD), which works closely with the Attorney General’s Office, was asked: ‘How much have you paid out in legal costs and disbursements to your lawyers and theirs for both cases [the apology/compensation claim and the refusal to prosecute an MI6 official]?’

The GLD replied: “Total legal costs for [the government] were £4,411,147.20, of which £2,849,522.17 were disbursements. The legal costs paid to lawyers for Mr Belhaj and Ms Boudchar were £6,995,007.23.

“It is not possible to provide further details in relation to this second figure, as [Her Majesty’s Government] negotiated some of these costs without having received a breakdown between fees and disbursements.”

The series of cases involved numerous judicial review challenges of government decisions and the Crown Prosecution Service’s conclusion not to charge Sir Mark Allen, MI6’s former head of counter-terrorism. Allen has always maintained his innocence.

The case was brought by the civil liberties organisation Reprieve, whose deputy director Katie Taylor said: “Abdul Hakim Belhaj and Fatima Boudchar were willing to settle for an apology all along, but rather than admit Britain’s role in their rendition, the government resisted coming clean for years – at astronomical cost to the taxpayer.

“This failed cover-up shows the need for a judge-led inquiry into British complicity in torture. If the prime minister has truly learned her lesson, as she wrote in her apology to the couple, she surely understands this is the only way to draw a line under this shameful era and prevent further ‘war on terror’ abuses.”

The government maintained that the figures were so high because the case, which began in 2011, lasted for so many years. It claimed that it had substantially negotiated down the legal fees paid.

Previous figures released had not included charges that were not invoiced at the time. The costs are far higher than earlier estimates.

The government maintains that since there was no admission of legal liability, it was reasonable that it should defend its position while protecting the UK public interest.