Dr Sentamu, the Church of England's second in command, urged the UN Human Rights Commission (UNHRC) to take legal action against the US - through the US courts or the International Court of Justice at The Hague - should it fail to respond to a report, by five UN inspectors, advising that Camp Delta at Guantanamo Bay should be shut immediately because prisoners there are being tortured.
The report was published on Thursday, as a senior High Court judge, Mr Justice Collins, stated that American actions over Guantanamo's Camp Delta do not "appear to coincide with that of most civilised nations". As a result of his ruling, three of eight British inmates held in the camp are to appeal to the Foreign Secretary Jack Straw to intervene with the Bush administration on their behalf.
Archbishop Sentamu's comments will strengthen the increasingly insistent international pressure for Guantanamo to be closed. Archbishop Desmond Tutu called for its closure, after similar appeals by Peter Hain, the Northern Ireland Secretary, and the UN secretary general Kofi Annan.
Dr Sentamu said the UNHRC should seek a writ of habeas corpus, compelling the US to bring those being detained at Guantanamo to court, to establish whether they are imprisoned lawfully and if they should be released.
"The American Government is breaking international law," he told The Independent. "The main building block of a democratic society is that everyone is equal before the law, innocent until proved otherwise, and has the right to legal representation. If the guilt of the prisoners in Guantanamo Bay is beyond doubt, why are the Americans afraid to bring them to trial? Transparency and accountability are the other side of the coin of freedom and responsibility. We are all accountable for our actions in spite of circumstances. The events of 9/11 cannot erase the rule of law and international obligations.
"The US should try all 500 detainees at Guantanamo, who still include eight British residents, or free them without further delay. To hold someone for up to four years without charge clearly indicates a society that is heading towards George Orwell's Animal Farm."
The Government has already managed to secure the release, in March 2004, of the four British nationals who were detained at Guantanamo Moazzam Begg, Feroz Abbasi, Martin Mubanga and Richard Belmar although only after guarantees they would be constantly monitored and face an investigation to ascertain whether they can be charged in this country.
Washington had claimed all four were "enemy combatants" who trained at camps run by al-Qa'ida. But they were released after UK police concluded there was not enough evidence to charge them with any offence. The men said they had been tortured at Guantanamo, allegations the US denied.
So far the Prime Minister appears unmoved by the growing sense of indignation brought on by the UNHRC report. He reiterated a statement first made a year ago that the base in Cuba was "an anomaly".
Sir Menzies Campbell, the acting Liberal Democrat leader, said: "This is not an anomaly which needs to be sorted sooner or later. This is an outrage that needs to be sorted out now. Guantanamo Bay has damaged the reputation of the US and its allies across the globe, and particularly in the Middle East."
The Attorney General, Lord Goldsmith, told the BBC the military tribunals proposed by Washington to try detainees at the base did not amount to a fair trial "by standards we would regard as acceptable". But last night, Donald Rumsfeld, the US Defence Secretary, rejected Mr Annan's calls.
"He's just flat wrong. We shouldn't close Guantanamo," he said. "We have several hundred terrorists, bad people, people who if they went back out on the field would try to kill Americans ... To close that place and pretend that really there's no problem just isn't realistic."
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