In dramatic scenes in the Commons, the Prime Minister faced down heckling from his own side and declared defiantly that the war on terrorism would continue until the threat was dealt with.

His patience snapped in the final minutes of Prime Minister’s Questions after Lynne Jones, a left-wing Labour MP, goaded him by claiming he had not regarded Saddam Hussein as a threat until President Bush’s “axis of evil” speech last year. Mr Blair began a passionate account of the enforcement by British troops of the no-fly zone and sanctions on Iraq and his own warnings of the danger of weapons of mass destruction when he was interrupted by Labour MPs’ shouts.

He rounded on Diane Abbott, another leftwinger, who called out to him defiantly: “Who’s next?”

“After we deal with Iraq we then do, yes, through the United Nations, have to confront North Korea about its weapons programme,” Mr Blair told her as the level of heckling rose. “We have to confront those companies and individuals trading in weapons of mass destruction.”

He wheeled on another MP who shouted out: “When do we stop?”

“We stop when the threat to our security is properly and fully dealt with,” Mr Blair responded.

The exchanges came after a tense session dominated by Iraq in which Iain Duncan Smith, the Conservative leader, who has previously fully supported the Government’s stance, for the first time referred to doubts among voters over the policy. The British people knew Saddam was an evil dictator who had attacked his neighbours, gassed his own people and was responsible for countless human rights abuses, Mr Duncan Smith said.

“But they also want to know more detail about the potential threat he poses to this country and our citizens,” the Leader of the Opposition said.

He urged Mr Blair to follow the lead of President Bush in disclosing more details of what his intelligence services knew about Saddam’s weapons programmes and his terrorist links. “Will he also publish further information and do you accept the British people deserve the fullest possible information on the scale and nature of the threat we clearly now face?” Mr Duncan Smith asked.

Mr Blair was further angered when Charles Kennedy, the Liberal Democrat leader, suggested that all the decisions on war with Iraq would be taken by President Bush because British troops sent to the Gulf would be under American command structures.

The Labour MP Tam Dalyell was cheered by Liberal Democrats and some Labour MPs for demanding a vote in the Commons before British troops were put under American command.

Mr Blair said the command structure would be the same as that used successfully in Afghanistan and Kosovo and confirmed that there would be a Commons vote before military action unless it would put British troops in danger.

“The idea that we have a record of taking this action without the House being consulted is nonsense,” Mr Blair said.

The Prime Minister said that Hans Blix, the UN Chief Weapons Inspector, had clearly found Saddam to be “in breach” of the UN resolution requiring him to co-operate and disarm and told Labour MPs who urged a solution through the UN to support their enforcement.

He told MPs: “If you read Dr Blix’s report, who can doubt that Saddam is in breach of his UN obligations? Let us follow the UN route, let us implement the resolution and let us make sure the threat to our security from these weapons is properly dealt with.”

• Depleted uranium munitions will form part of the armoury taken to the Gulf by British troops preparing for a possible war with Iraq.

  Adam Ingram, the Armed Forces Minister, said that weapons containing the substance — blamed by veterans’ groups for ill health suffered by soldiers after the first Gulf War — would be available.

  Scientists have found that a number of people might suffer kidney damage after exposure to depleted uranium from exploded weapons. Depleted uranium, or DU, is the “waste” left over from the process used to produce the fissionable material used in nuclear weapons.

  It is very heavy, having nearly twice the density of lead — which makes it ideal for use as “penetrators” in armour-piercing shells. It was used widely in the Gulf War and the conflicts in Bosnia and Kosovo.

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