THE US has threatened to withhold intelligence from Britain if evidence of the alleged torture of a British resident held at Guantanamo Bay is made public.

Details of how the "terrorist" detainee was allegedly tortured - and what British intelligence services knew about it - must remain secret because of the American threats, the High Court ruled yesterday.

Lord Justice Thomas and Justice Lloyd Jones said lawyers for the Foreign Secretary had told them that the threat by the US still applied under President Barack Obama. Oppostion MPs accused the Government of giving in to blackmail.

The disclosure that the US has threatened to re-evaluate sharing intelligence with Britain came just 24 hours after new US Secretary of State Hillary Clinton lavished praise on the special relationship between the two countries.

Noting that it is contrary to the rule of law not to release the evidence, the judges said that it must remain secret otherwise "the public of the United Kingdom would be put at risk".

Binyam Mohamed, a British resident held at the base on Cuba, has launched a High Court challenge in London seeking that documents detailing his treatment to be made public.

But the judges ruled that Foreign Secretary David Miliband had said that releasing the evidence could lead to the US "revaluating" its intelligence sharing with the "real risk that it would reduce the intelligence provided".

The judges added: "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 called on the Obama administration to reconsider. "If the information in the redacted paragraphs, which we consider so important to the rule of law, free speech and democratic accountability, is to be put into the public domain, it must now be for the United States Government to consider changing its position or itself putting that information into the public domain."

The British Foreign Office insisted that it had not "engaged in detail" with the new administration about the judgment in what appeared to be an attempt to minimise the embarrassment to Mr Obama.

The ruling discloses that the secret documents at the centre of the case - seven paragraphs amounting to 25 lines - "give rise to an arguable case of torture or cruel, inhuman or degrading treatment" against Mr Mohamed.

It is also said that a British intelligence official may have been present when Mr Mohamed alleges that he was tortured. This raises the prospect of charges being brought against British officials.

David Davis, the former British shadow home secretary, called for the Government to explain what had happened. He said that the US threat was a "matter of utmost importance" and urged Mr Miliband to "come clean".

Liberal Democrat leader Nick Clegg said: "There is no other term for what the US intelligence services are doing than blackmail."

Clive Stafford Smith, Mr Mohamed's lawyer, accused Britain of "capitulation to blackmail, pure and simple".

Last night Mr Miliband said that Britain's continuing intelligence relationship with the US depended on mutual trust. "There has been no threat from the United States to `break off' intelligence co-operation," he told Channel 4 News.

"Intelligence co-operation depends on confidentiality. We share our secrets with other countries and they share their secrets with us. The founding principle for us and for them is that we can trust the confidentiality of that relationship.

``In this case, the United States made it clear, in documents that have been published, that there would inevitably be serious and lasting harm if that fundamental principle was breached."

Mr Miliband said that there was no indication that the US position had changed under Mr Obama.

He added: "We never condone or authorise the use of torture."

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