Britain can no longer believe what Americans tell us about torture, an MPs' report to be published today claims. They also call for an immediate investigation into allegations that the UK government has itself 'outsourced' the torture of its own nationals to Pakistan.

In a damning criticism of US integrity, the House of Commons Foreign Affairs Committee said ministers should no longer take at face value statements from senior politicians, including George Bush, that America does not resort to torture in the light of the CIA admitting it used 'waterboarding'. The interrogation technique was unreservedly condemned by Foreign Secretary David Miliband, who said it amounted to torture.

A change in approach would have implications for extradition of prisoners to the US, especially in terror or security cases, as the UK has signed the UN convention which bars sending individuals to nations where they are at risk of being tortured. During waterboarding, a person is tied to a board with their feet raised and cellophane wrapped around the head. Water is then poured on to the face, causing the victim to start to drown.

Today's committee report said there were 'serious implications' of the striking inconsistencies between British ministers continuing to believe the Bush administration when it denies using torture. '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. 'We also recommend that the government should immediately carry out an exhaustive analysis of current US interrogation techniques on the basis of such information as is publicly available or which can be supplied by the US.'

It also urges the government to press the US authorities for information on whether any American military flights landing in the UK were part of the 'rendition circuit', even if they did not have detainees on board at the time.

The government has repeatedly accepted US assurances that UK territory has not been used for 'rendition', the extra-judicial transfer of suspects between countries. But in February, Miliband told the Commons he had been informed by the US that two rendition planes refuelled on the British territory of Diego Garcia in the Indian Ocean.

The MPs also urged the Foreign Office to investigate a Guardian report that six British nationals claimed to have been detained and tortured by the ISI, Pakistan's intelligence agency, where they were also interrogated by British intelligence officers. Foreign Minister Lord Malloch-Brown told the committee: 'We absolutely deny the charge that we have in any way outsourced torture to Inter-Services Intelligence [ISI] as a way of extracting information, either for court use or for use in counter-terrorism.'

The report also called on the Foreign Office to seek consular access to all British citizens, including those of dual nationality, detained in Pakistan and asked for an explanation from ministers why one of those detained was apparently denied consular access but was visited by a British official, who may have been an intelligence officer.