UK troops have found evidence "categorically" proving Iraq is ready to use chemical and biological weapons, Defence Secretary Geoff Hoon says.
Coalition forces fear Iraq may use chemical weapons
Mr Hoon said it had first become known from Iraqi PoWs that protective gear had been issued to troops in the south of the country.
But he said fresh evidence turned up over the last few days had proved the regime's willingness to use weapons of mass destruction.
Mr Hoon showed footage of British troops from the Royal Irish Regiment uncovering gas masks and protective suits, said to number more than 100, in a command post in the Rumaila oil field.
US and UK officials have consistently suggested that precautions against chemical and biological attacks among Iraqi soldiers are clear pointers that the regime plans to use such weapons.
Officials argue that precautions were not to counter the threat of coalition attacks, as the Iraqis would know the UK and US forces in the Gulf do not possess chemical and biological weapons.
Mr Hoon said: "We do have evidence that the Iraqi regime is prepared to use weapons of mass destruction.
There's an outside chance [the Iraqis] were preparing for somebody else to use weapons on their troops.
"We already knew from Iraqi prisoners of war that protective equipment was issued to southern Iraqi divisions.
"British forces have made significant discoveries in recent days which show categorically that Iraqi troops are prepared for the use of such horrific
"I want to make it clear that any Iraqi commander who sanctions the use of such weapons of mass destruction is committing a war crime and will be held personally responsible for his action."
"Paperwork and other equipment" had been found in the command post search, Chief of Defence Staff Admiral Sir Michael Boyce said.
He added: "This kit is effective, well cared for and in good working order."
Mr Hoon conceded the discovery of the suits was "obviously not conclusive" proof Iraqi forces were set to use chemical or biological weapons.
But he added: "It's clearly indicative of an intention, otherwise why equip his own forces to deal with a threat which he knows we do not have?
"So it must only be to protect his forces from his own use of those weapons which we know he has."
Mr Hoon said no non-lethal chemical weapons, such as CS gas, had been used in the campaign and that Britain was fully signed up to the Chemical Weapons Convention which prohibited the use of such weapons in conflict.
A search in Rumaila turned up 100 suits
On Tuesday US marines said they had found crates full of nuclear, biological and chemical protection suits at a hospital complex near Nasiriya which had been used by Iraqi soldiers.
Andy Oppenheimer, an expert on chemical and biological weapons with Jane's Information Group, said there could feasibly be a number of reasons for Iraq keeping suits, although Mr Hoon's interpretation was the most obvious.
He told BBC News Online: "Everybody is trying to find the smoking gun that wasn't found earlier.
"There's an outside chance [the Iraqis] were preparing for somebody else to use weapons on their troops.
"But neither the US or Britain is supposed to have any of those weapons."
But Mr Oppenheimer said the US was known to have agents that could incapacitate troops.
He added: "You could say the Iraqis want to make it look like they could use a chemical weapon. It could be part of the policy of producing as much disruption as they can."
Speaking at a press briefing in the Ministry of Defence, the defence secretary also said it was possible 15 deaths in a Baghdad marketplace could have been caused by Iraqi fire.
"Although investigations continue into this tragic incident, it could clearly have been caused by fallout from the regime's anti-aircraft fire or the failure of one of the regime's own missiles," he said.
He condemned the release of footage of dead British troops and captured POWs.
"This is a flagrant and sickening breach of the Geneva Convention," he said.
"Sadly, this is typical behaviour of Saddam Hussein and his regime."