The UK Government is "appalled" by pictures of Iraqi prisoners being abused by US troops, No 10 has said.
Abu Ghraib prison was much feared in Saddam Hussein's era
Tony Blair's official spokesman said the way naked prisoners were tormented by troops directly contravened all the US-led coalition's policy.
He stressed the abuse by a few soldiers at the Abu Ghraib jail was not representative of coalition troops.
But Labour MP John McDonnell instead argued the coalition's occupation of Iraq was being discredited.
A US military investigation has recommended disciplinary action against several of its officers for the alleged abuse of Iraqi prisoners.
Brigadier General Janis Karpinski is among seven officers being investigated following claims that soldiers under their command mistreated detainees.
The officers have already been suspended from duty.
Photographs of naked, hooded men being subjected to mock torture have been broadcast on American television channel CBS TV.
The US military says it is appalled by the behaviour of its soldiers, but insists this is an isolated case.
Mr Blair's official spokesman said: "The US army spokesman has said this
morning that he is appalled, that those responsible have let their fellow
soldiers down, and those are views that we would associate the UK Government
He added: "This is not
representative of the 150,000 soldiers that are in Iraq, and they should not
judge the actions of the coalition as a whole on the actions of a few.
"But it is regrettable, to say the least."
Ann Clwyd, Mr Blair's special envoy in Iraq and a supporter of the military action, told BBC Radio 4's Today programme: "These [pictures] are absolutely terrible."
The Labour MP said she had visited Abu Ghraib prison and raised concerns with the general in charge - although this was not the officer now being investigated.
"I was particularly concerned that so many prisoners are being held there over a long period of time, that their families quite often don't know they are even there," she said.
Families often queued outside the jail as they tried to discover whether their relatives were being detained there.
Ms Clwyd said she had raised worries about Abu Ghraib on her recent visit to the White House.
A "very senior" White House official had told her US troops did not abuse Iraqi prisoners.
She continued: "The people in charge did not know this was going on."
The MP also denied the pictures could cause a perception that the coalition was adopting tactics similar to those used by the former Iraqi regime.
"On a small number of cases, horrible that they are, you cannot compare that with the tens of thousands of people that Saddam Hussein was responsible for executing and torturing," she added.
Mr McDonnell, from the anti-war Socialist Campaign Group of Labour MPs, said the pictures underlined the need for a United Nations peacekeeping force to take over from the US-led coalition.
"They are very, very shocking. I think this is further evidence which builds up on top of the attack on Falluja which is discrediting the American occupation of Iraq," he said.
Conservative shadow foreign secretary Michael Ancram welcomed the "swift and firm" moves to tackle those allegedly behind the abuse.
behaviour is unacceptable and very damaging to building confidence in Iraq," he said.
The Ministry of Defence said the abuse allegations were a "purely American matter".