Andrew Tyrie says it is essential to establish who authorised secret operations ‘to draw a line under this sorry episode’

A senior Conservative MP has described the continuing cover-up of Britain’s complicity in the kidnapping and torture of detainees in the “war on terror” – and of who authorised it – as a shocking scandal that must be resolved without further delay.

Andrew Tyrie, the chair of the all-party parliamentary group on extraordinary rendition, made clear that an answer to the key question – who knew about the secret operations – was getting closer.

Tyrie, also chair of the Commons liaison committee of senior backbenchers and the Commons Treasury committee, was responding on Wednesday to the Guardian’s disclosure that the former head of MI5 was incensed when she discovered the role played by MI6 in abductions that led to suspected extremists being tortured.

Blair government's rendition policy led to rift between UK spy agencies Read more

Lady Eliza Manningham-Buller was so angry that she threw out a number of her sister agency’s staff and banned them from working at MI5’s headquarters at Thames House in London.

She wrote to Tony Blair, then the prime minister, to complain about the conduct of MI6 officers, saying their actions had threatened Britain’s intelligence gathering and may have compromised the security and safety of MI5 officers and their informants.

Her letter was discovered by investigators examining whether British intelligence officers should face criminal charges over the rendition of the exiled Libyan opposition leader Abdul Hakim Belhaj.

“This letter strongly suggests Tony Blair, the former head of MI6 Sir Richard Dearlove, and Eliza Manningham-Buller, the head of MI5, all knew that secret agents were engaged in the rendering, and possibly subsequent maltreatment, of prisoners,” Tyrie told the Guardian. “It is now essential to establish who authorised this rendition. The chances of it not having been authorised would appear low. Were it unauthorised it would be criminal.”

Section 7 of the 1994 Intelligence Services Act protects MI6 officers from prosecution for actions anywhere in the world that would otherwise be illegal. They would be protected as long as their actions were authorised in writing by the foreign secretary, who is the minister responsible for MI6. At the time the office was held by Jack Straw.

Facebook Twitter Pinterest Eliza Manningham-Buller. Photograph: D Dudley/Pacific/Barcroft

Tyrie told the Guardian: “It is a scandal and shocking that, after nearly a decade of demanding answers, the public still don’t know the scope and limits of the UK’s complicity in kidnap and torture. Public confidence in the security services has been eroded as a consequence. We need them. It is now essential that the prime minister ensures that the ISC [parliament’s intelligence and security committee] are able to get to the bottom of this, and without delay. Only by doing so can a line be drawn under this sorry episode.”

Tyrie clashed with David Cameron at a meeting of the liaison committee in January, arguing that the ISC should have more effective powers to scrutinise the security and intelligence agencies.

Separately, a leading human rights group said Manningham-Buller was “right to be disgusted” over MI6’s involvement in secret rendition – the seizure and interrogation of suspected extremists.

Cori Crider, a lawyer at the international human rights organisation Reprieve, said: “You know MI6 under Blair’s government were running amok when their role in CIA kidnap operations turned even the stomachs of MI5. Yet now, according to this report, officials are exercising mass tactical amnesia over who signed off the most appalling abuses in the ‘war on terror’. The notion that ‘the CPS [Crown Prosecution Service] cannot bring a charge against a government policy’ of torture is obviously wrong.”

Crider added: “Lady Manningham-Buller was right to be disgusted. The rendition of the Belhaj and al-Saadi families to Libya wasn’t just illegal – it broke every value Britons hold dear. It’s a damning assessment when even the hard-nosed head of MI5 could see that delivering a pregnant woman and four children to Gaddafi’s dungeons was wrong, pointless, and made Britain less safe. There clearly is a case to answer here, and Reprieve aren’t the only ones who think so. We eagerly anticipate the long-delayed decision of the CPS.”

Facebook Twitter Pinterest Reprieve’s Cori Crider. Photograph: Pablo Porciuncula/AFP/Getty Images

A spokesperson for Leigh Day, Belhaj’s lawyers, said: “These revelations are extraordinary, we hope that the CPS does take the decision to prosecute those allegedly responsible for illegal acts of rendition. The courts can then determine the full extent of the role played by the British government, and its security services, in sending our client Abdul Hakim Belhaj, along with his pregnant wife, back to Libya to be imprisoned and brutally tortured.”

Though government sources in the UK and US claim Blair and Straw knew about the rendition, both men have denied wrongdoing, saying they either did not know of the MI6 operation or had no recollection of it.

Manningham-Buller’s letter caused a serious and prolonged breakdown of trust between Britain’s domestic and foreign spy agencies provoked by the Blair government’s support for rendition.

Belhaj, a critic of the former Libyan dictator Muammar Gaddafi, was seized in Bangkok in March 2004 in a joint UK-US operation and handed over to the CIA. He alleges the CIA tortured him and injected him with “truth serum” before flying him and his family to Tripoli to be interrogated.

Scotland Yard has concluded its investigation into the alleged involvement of intelligence officers and officials in Libyan rendition operations and an announcement about whether or not to prosecute is imminent.

Whitehall sources have told the Guardian that police and prosecutors have been reviewing the issue for months. They say investigators have been frustrated by potentially key witnesses saying they were unable to recall who had authorised British involvement in the rendition programme, who else knew about it, and who knew the precise details of the Belhaj abduction.

When the Libyan renditions came to light, Straw said: “No foreign secretary can know all the details of what its intelligence agencies are doing at any one time.” He has been interviewed by the police but only as a potential witness.

Government officials, insisting on anonymity, said MI6 was following “ministerially authorised government policy”. Blair said he did not have “any recollection at all” of the Belhaj rendition.