Britain's Deputy Prime Minister Nick Clegg has said the invasion of Iraq was illegal, throwing into confusion the coalition government's policy.
Clegg's comments on Wednesday angered some Conservative MPs, many of whom, including Prime Minister David Cameron, had voted for the 2003 invasion, The Telegraph reported.
The Liberal Democrat leader was speaking in parliament while deputising for Cameron, who is on an official visit to the US.
His remarks came as Clegg clashed with former foreign secretary Jack Straw. Speaking about Straw he said: "Maybe he one day - perhaps we will have to wait for his memoirs - could account for his role in the most disastrous decision of all, which is the illegal invasion of Iraq."
The Liberal Democrats were the only mainstream party to oppose the decision to topple Saddam Hussein.
Downing Street unconvincingly claimed that Clegg was allowed to speak in a personal capacity. In an attempt to defuse the row, it said that the Iraq inquiry, led by Sir John Chilcot, would declare whether the invasion in March 2003 was illegal.
But hours later a spokesman for the inquiry made it clear that Sir John would not make a conclusion on whether the US-led invasion, which was backed by 45,000 British personnel, was legal, the report said.