The latest report from the Iraq Survey Group has re-ignited the row over Saddam Hussein's weapons of mass destruction.

Details of the report were set to be published in Washington later on Wednesday.

But it was expected to conclude that no evidence had been found of Iraqi chemical, biological or nuclear weapons.

Prior to the war, the UK government's intelligence dossier had warned that Iraq had WMD munitions available for launch "within 45 minutes".

The subsequent failure to find any such weapons has been behind a collapse of trust in the prime minister and his government.

And the latest findings were set to add to Tony Blair's embarrassment.

Ahead of the announcement, the foreign secretary sought to defend the government's position.

Speaking in Iraq, Jack Straw said the report would prove that "in terms of his intention" Saddam posed an "even starker" threat than thought.

"I personally am in no doubt whatever that had we walked away from Iraq and left Iraq to Saddam, Saddam would have indeed built up his capabilities, built up his strength and posed an even greater threat to the people of Iraq and the people of the region than before," he said.

The Conservatives said the expected ISG conclusions would come as "no surprise".

"I don't think it alters the case for war one way or another personally, but I think it is difficult for the Americans and for the prime minister to explain," shadow defence secretary Nicholas Soames told the BBC.

Liberal Democrat foreign affairs spokesman Sir Menzies Campbell said the report would prove that the policy of containment and deterrence should have been left in place.

"It most certainly does not provide any support for the government's view that the threat from Saddam Hussein was so acute that only immediate military action would do," he said.

"Brick by brick the government's case for going to war is being demolished."

And former foreign secretary Robin Cook added to the government's discomfort by saying the report would undermine the case for going to war.

"It comprehensively establishes that Iraq had no stockpile, no biological agents, no chemical feedstocks, no plants to manufacture them and no delivery systems to fire them," he said.

"Saddam was no threat to us and had no weapons of mass destruction to pass to terrorists. Brushing the UN inspectors aside in order to go to war on false intelligence was a colossal blunder."

Meanwhile, Plaid Cymru, which has been leading a campaign for the prime minister's impeachment, said the study would boost their case.

MP has today restated the case for the Prime Minister’s impeachment following news that the Iraq Survey Group has concluded that Saddam Hussein had no weapons of mass destruction.

"Had Tony Blair and George Bush allowed Hans Blix and his team of UN weapons inspectors to continue their work, thousands of innocent civilians in Iraq would not have been killed and Iraq would not be experiencing the bloodshed and chaos which we witness daily on our television screens," said Welsh nationalist parliamentary leader Elfyn Llwyd.

"When ordinary people in ordinary jobs are found to have made serious mistakes, and even worse, when they are found to have misled or lied, they are forced to face the consequences.

"Tony Blair believes he is above this kind of accountability. It is now up to parliament to show that he can no longer get away with such misconduct and impeachment is the only way to achieve this."