David Miliband insisted today that Britain was unable to publish information regarding the torture of a former British resident now held at Guantanamo Bay because it would have violated an intelligence-sharing agreement with the United States.

The Foreign Secretary said that breaching American trust by publishing classified information would have caused “real and significant damage to the national security and international relations of this country”.

He denied claims, however, that Washington had applied diplomatic pressure on Britain to keep secret Binyam Mohamed's alleged mistreatment in clandestine US jails in Pakistan, Afghanistan and Morocco.

Mr Miliband was forced to make the statement after two British judges released a damning ruling on Mr Mohamed's case yesterday. The judges complained that they could not release details of Mr Mohamed's alleged mistreatment and Britain's role in it, even though it was in the interests of justice, because America had threatened to withdraw intelligence co-operation from Britain and this could put British lives at risk.

"It was and remains (so far as we are aware) the judgment of the Foreign Secretary that the United States Government might carry out that threat and this would seriously prejudice the national security of the United Kingdom," the judges wrote.

Lord Justice Thomas and Mr Justice Lloyd Jones added that the information they wanted to release - about 25 lines of text about Mr Mohamed's case, taken from official documents from American intelligence agencies - posed no threat to British or US security, but was potentially "embarrassing" as it did add to up to "an arguable case of torture or cruel, inhuman or degrading treatment", in contravention of national and international law.

Mr Mohamed claims that British spies interviewed him during the time he alleges he was having his chest and penis cut with a scalpel and stinging liquid poured into the wounds, and that they passed on detailed personal information about him to his torturers.

Mr Miliband said today that it was a longstanding Government policy “that we never condone, authorise or cooperate in torture”. He said that the information in the dossier had been shared with Mr Mohamed’s US lawyers but should not be openly published.

He told MPs: “The information in question is available to his US legal counsel. As the court said ’upholding the rule of law is most unlikely to depend on making the information public’.

“The issue at stake is not the content of the intelligence material but the principle at the heart of all intelligence relationships - that a country retains control of its intelligence information and it cannot be disclosed by foreign authorities without its consent.

“That is a principle we neglect at our peril,” he said. “In this case it was US intelligence in a UK court. It could easily have been British intelligence in a foreign court.”

The Conservatives, the Liberal Democrats, human rights experts, and lawyers and family of Mr Mohamed have all decried this, claiming that allegations of torture were too serious ever to be suppressed or condoned.

"No British government should participate in or condone torture under any circumstances," said William Hague, the Shadow Foreign Secretary. “We hope the new US administration will look again at this decision, particularly since the judge concluded that there were no security reasons for the material not to be made public.”

Mr Hague said he hoped that any British agent thought to have condoned or participated in torture would be prosecuted.

Nick Clegg, the leader of the Liberal Democrats, said that the case smacked of cover up.

"Torture is unacceptable under all circumstances, and that is what we should be concentrating on. There is no excuse not to make that information public," he told BBC Radio 4's Today programme.

Mr Mohamed's brother, Dr Benhur Mohamed, said that the decision to block the release of information about his brother's detention was "unacceptable". He added that he had written to Mr Miliband asking him to help his brother, but was bitterly disappointed to have received no reply.

"I was truly begging him to do something about Binyam, that was my plea, but I didn't hear anything," Dr Mohamed told BBC Radio 5 Live.

"I feel very sad, I feel betrayed. It's very cruel from a person who is elected by the people to protect humanity and freedom and the rule of law."

Dr Mohamed claimed that his brother, who is not currently accused of any crime after the US dropped charges that he was involved in an alleged dirty bomb plot, was a "quiet" and "helpful" person. "He is very supportive and very considerate. He is not the kind of person who would want to hurt anybody," he said.

Lt Colonel Yvonne Bradley, Mr Mohamed's US military lawyer, who visited him in Guantanamo Bay last week, said that America wanted to save face. "What the US is doing right now is not so much about national security or intelligence - it's about being embarrassed," she said.

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