Adam Ingram, the armed forces minister, and Lieutenant General Robin Brims, Commander Field Army in 2006, had told the Joint Committee on Human Rights that hooding and sleep deprivation were forbidden.But the committee said the assurances appeared to be false, and not all troops had known these and other "conditioning techniques" were banned.
It claimed there were "discrepancies" between the testimony of Mr Ingram in 2004 and Lt Gen Brims in 2006, and what had happened on the ground.
Des Browne, the Defence Secretary, said the committee's concerns would be investigated as part of an imminent public inquiry into the death of Baha Mousa.
Mr Mousa, an Iraqi hotel worker, died in British custody in 2003. He suffered asphyxiation and was found to have 93 injuries on his body.
Earlier this month, the Ministry of Defence (MoD) agreed to pay almost £3million in compensation to his family and nine Iraqi men after admitting breaching human rights.
Last year Corporal Donald Payne was jailed after pleading guilty to inhumane treatment at a court martial. Six other soldiers were acquitted of the charges they faced.
Conditioning techniques were banned during the Northern Ireland troubles in the 1970s, but a report by Brigadier Robert Aitken in January said changes were needed to rectify serious flaws in soldiers' training for dealing with Iraqi prisoners.
In a report published yesterday, the Joint Committee on Human Rights complained: "We have yet to receive an explanation from the Ministry of Defence for the discrepancies between the evidence given to the Joint Committee in 2004 and 2006 on the use of prohibited conditioning techniques and the facts which have emerged from the Payne court martial and the Aitken report."
The committee, which comprises members of the Commons and Lords, demanded a "detailed explanation of the discrepancies" be produced as soon as possible after the inquiry.
Last week the Defence Secretary announced the terms of reference for the public inquiry into the death of Baha Mousa.
"Those terms of reference are sufficiently broad to enable the inquiry to conduct a thorough examination of the circumstances surrounding that death and the committee has acknowledged that many of the concerns it has raised in its report may be investigated by the inquiry," Mr Browne said yesterday.
"However, it is not possible for us to comment further on issues or events likely to be investigated under the inquiry, including past evidence given to the committee, until the inquiry has concluded."
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