The International Committee of the Red
Cross says it had expressed concern to the UK about Iraqis under British detention in Iraq.
The Daily Mirror published photos allegedly showing prisoner abuse
The claim comes after it said it had repeatedly asked the US to take action over abuses of prisoners by US soldiers at Iraq's Abu Ghraib prison.
Both US and British media have published several photographs showing alleged abuse by coalition soldiers.
The UK Ministry of Defence has said it is investigating the abuse claims.
The ICRC's director of operations Pierre Kraehenbuehl said "concerns and recommendations" had been made to British authorities.
However he declined to be specific about when or what issues were addressed because the ICRC report to British authorities has not been made public.
A spokesman for the Ministry of Defence later said the claims by the ICRC were contained in an interim report that dated back to before the British opened their own detention centre at Sheibah, south of Basra.
Mr Kraehenbuehl added that British forces were regularly in touch with the ICRC, and would take on board any concerns the committee may have.
"If they raise particular points, we would take action to meet their concerns and to meet our obligations under the Geneva Convention and international law," he said.
Officials from the Foreign Office and Downing Street were "taken aback" by the ICRC's statement, and were unable to "confirm, deny or respond", said BBC political correspondent Carole Walker.
The Conservatives on Saturday demanded that the government should reveal exactly when it became aware of the abuse claims.
Tory Shadow Defence Secretary Nicholas Soames said: "If, as it seems, the International Committee of the Red Cross raised the possibility of the mistreatment of Iraqi prisoners with the British Government quite some time ago, then this must be a matter of gravest concern.
"Number 10, the Secretary of State for Defence and the Foreign Office must say whether or not these questions were indeed raised with them and what actions were subsequently taken".
Mr Soames demanded that the secretary of state for defence, Geoffrey Hoon, should make a full and detailed statement on this and other allegations about treatment of Iraq abuse to parliament on Monday.
The Daily Mirror, which published photos allegedly showing abuse by UK soldiers, revealed more details in Saturday's paper.
Questions have been raised over the authenticity of the photos.
But a soldier with links to the Queen's Lancashire Regiment - the third to talk to the newspaper - told of "appalling beatings" of prisoners.
During one incident, "Soldier C" told the Mirror, a corporal placed a sandbag over a suspect's face and poked his fingers in the victim's eyes until he screamed with pain.
In the US, pressure is mounting on US Secretary of Defence Ronald Rumsfeld over his handling of the affair.
The Red Cross has been visiting Abu Ghraib every five or six weeks since last year.
The ICRC, which traditionally does not speak publicly about its prisoner visits, will not say exactly what problems were found at Abu Ghraib.
The most recent visit took place at the end of March.