Assurances from the US that it does not use torture can no longer be relied upon by the British authorities, an MPs' report has warned.
Ministers have previously been willing to take on face value statements from senior American politicians including President George Bush that the US does not resort to torture, said the House of Commons Foreign Affairs Committee.
But the committee said that the stance should be dropped in the light of CIA admissions that it subjected three detainees to "waterboarding", an interrogation technique which Foreign Secretary David Miliband has said amounts to torture.
Such a change in approach would have implications for the extradition of prisoners to the US, particularly in terror cases, as the UK is a signatory to a United Nations convention barring the return of individuals to states where they are at risk of being tortured.
During waterboarding, a detainee is bound to a board with feet raised and cellophane wrapped around his head. Water is poured onto his face in a process that, if uninterrupted, would lead to drowning.
In February this year, the US Director of National Intelligence. Michael McConnell, told a Senate committee that waterboarding was "a legal technique used in a specific set of circumstances".
The following month, President Bush vetoed a bill which would have banned the practice, saying he did not want to deprive agents of valuable tools in the war on terror.
In April, Mr Miliband told the House of Commons: "I consider that water-boarding amounts to torture. The UK unreservedly condemns the use of torture."
The report by the Foreign Affairs Committee welcomed Mr Miliband's statement, but said it gave rise to "serious implications". There appeared to be a "striking inconsistency" in ministers' continued acceptance of the Bush administration's denial that it uses torture.
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"Given the clear differences in definition, the UK can no longer rely on US assurances that it does not use torture, and we recommend that the Government does not rely on such assurances in the future," said the committee in its report on the Foreign Office's annual human rights report.
