A parliamentary committee in Britain has recommended that the government should no longer rely on assurances by the United States that it does not use torture.
The Foreign Affairs Committee says the two countries have clear differences in their definitions of torture and it urged the UK to check US claims.
It recommended the government carry out an "exhaustive analysis of current US interrogation techniques."
The committee highlighted the technique of "water-boarding" - a practice which simulates drowning.
The US describes it as "a legal technique used in a specific set of circumstances" and President Bush has refused to ban it.
However, the UK Foreign Secretary David Miliband said it is torture and "the UK unreservedly condemns the use of torture."
In its report, the committee said: "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."
The MPs challenged the government to check more actively that Britain had not been used by the Americans for so called "rendition" flights - when detainees are taken to countries where bans on torture may not apply.
The UK had repeatedly accepted assurances that it had not, but it was discovered earlier this year that two rendition planes refuelled on the British territory of Diego Garcia in the Indian Ocean.
The MPs stressed the UK had a "legal and moral obligation" to ensure no more of these flights landed on British territory.