Ex-Foreign Secretary Robin Cook has pressed the government to publish a Red Cross report raising concerns about UK troops abusing Iraqi prisoners.
The Daily Mirror published photos allegedly showing prisoner abuse
The call came as opposition parties demanded ministers reveal what they knew and when about the alleged abuses.
The government has confirmed it received the Red Cross report in February - weeks before claims surfaced in the press.
A spokesman said action had been taken, but declined to give details.
The Ministry of Defence (MoD) says it is "not likely" to publish the Red Cross report, saying it is confidential.
But Mr Cook said it was important that the government did make the report public.
"Until they do, really we cannot see what independent people are saying about the problem and how severe it is," Mr Cook told Breakfast with Frost.
The Labour MP said Tony Blair was a "victim of a tragedy" because he was now finding it hard to get away from his mistake in Iraq and focus on his impressive domestic record.
"There will come a time when he has to ask himself whether he can succeed in that task or whether someone else should do it," added Mr Cook.
The Conservatives and Liberal Democrats are calling on the Defence Secretary Geoff Hoon to make a statement to MPs in the Commons - something he is understood to be considering.
Shadow foreign secretary Michael Ancram said: "It is imperative that the
government comes to the House of Commons at the earliest opportunity to explain
what it knew and what it did about it."
Three Britons questioned inmates at the Abu Ghraib prison
Liberal Democrat leader Charles Kennedy also said the government must now make
clear "what it knew and when".
The allegations had done "enormous damage", he said.
"It is important to reassure both the Iraqi people and Muslims from this country that if additional allegations are true they will be
dealt with swiftly and firmly."
The Red Cross declared on Friday that it had previously warned the UK of abuses.
Spokesman Roland Huguenin-Benjamin told Sky News on Sunday: "The concern we have been expressing for a year now deals with a general
pattern of mistreatment of detainees.
"We were warning of the fact that the treatment given to prisoners and in
particular the way they were prepared for interrogation is not acceptable from
the point of view of the Geneva Convention."
New claims of abuse emerged in the UK newspapers on Sunday.
The Sunday Times says soldiers from the Royal Regiment of Fusiliers are facing possible charges over alleged
serious sexual assaults and abuse of prisoners.
The Independent on Sunday reported eight new cases of British soldiers allegedly shooting dead eight Iraqi civilians in cold blood.
And the MoD confirmed that three British military staff spent several months this year questioning inmates at the American-run Abu Ghraib prison outside Baghdad - at the centre of claims of abuse by US troops.
An MoD spokesman said the three had been seeking information which would help the coalition and were unaware of the abuses there.
The Daily Mirror has published a series of photos over the last week, allegedly detailing abuse of Iraqi prisoners by British troops.
The Mirror stands by the photos despite doubts voiced about their authenticity.