Ministers are being accused of disarray about when they first heard of abuse claims against British troops.
Opposition parties are also demanding an apology from Armed Forces Minister Adam Ingram for misleading MPs - a charge rejected by his officials.
Defence Secretary Geoff Hoon argues the important thing is that all allegations were immediately investigated.
But Foreign Secretary Jack Straw has said ministers should have seen a Red Cross report on abuse claims earlier.
Two reports have emerged this week from human rights groups: the Red Cross concerns about Iraqi prisoners, produced confidentially in February, and Tuesday's Amnesty International report about civilian casualties.
Last week the armed forces minister told MPs he had not received any reports about concerns about the treatment of detainees.
Amnesty says it was surprised by that answer as it sent Mr Ingram a dossier about its worries in November last year.
Conservative shadow defence secretary Nicholas Soames told BBC Radio 4's World At One: "If indeed Amnesty are correct in what they say, I'm very
much afraid to say that I think that Adam Ingram may have materially misled the
House of Commons."
He said the minister was "straightforward and honourable" and would want to explain to MPs what he had meant.
Mr Hoon said his minister would use a Commons appearance on Thursday to clarify his comments.
"I think it will help everyone that if he makes clear ... that he was asked a
question about detainees," said Mr Hoon.
"And with the exception of a single letter that I
received around a year ago, the cases highlighted by Amnesty International have
not been about detainees."
Mr Hoon has said he did not receive the Red Cross report until last week because all its claims were already being investigated.
In the Commons, the foreign secretary said: "With the benefit of hindsight, it should have been made available to ministers but it happens it was not."
The Conservatives are demanding Mr Straw explain to MPs confusion over whether Sir Jeremy Greenstock, then Britain's special representative in Iraq, saw the report.
Downing Street and Mr Hoon said Sir Jeremy had seen the dossier, but Mr Straw said he had not.
On Tuesday afternoon, the prime minister's spokesman explained it had been passed to Sir Jeremy's legal advisers and had been acted upon.
"The confusion arose because we thought Sir Jeremy had read that report but in actual fact, he hadn't," he said.
The No 10 spokesman refused to say whether Mr Blair had known about abuse allegations made against US troops before they were published in the media.
He added: "If the prime minister knew of anything which was going wrong he would of course act accordingly.
"The prime minister has always made it clear that mistreatment of any kind is wrong and counterproductive."
Liberal Democrat foreign affairs spokesman Sir Menzies Campbell said: "The House of Commons is entitled to a clear and specific account of the
paper chase relating to the Red Cross report.
"So long as ministers appear to be at sixes and sevens, MPs are denied an
opportunity to make an informed judgment."