Tony Blair has warned that failing to act against Saddam Hussein could have "devastating consequences" for the people of Iraq.

The claim came as the prime minister faced growing Commons hostility to a war with Iraq.

On the day a poll revealed that 45 per cent of voters were against a war in any circumstances, Blair was repeatedly challenged on his stance.

A series of Labour backbenchers joined forces with Liberal Democrat leader Charles Kennedy to warn him against a military conflict.

But the prime minister said that opponents of military action should be aware of the moral consequences of backing away from the use of force.

Confronting critics of his hardline stance, he admitted that "innocent people die as well as guilty in a war".

Keeping sanctions would also be "a moral choice with bad and devastating consequences for the Iraqi people" said Blair.

The prime minister insisted that the UN had to be "very careful we do not get sucked back into the situation we had in the 1990s when inspectors were in there for years".

"The UN has to be the way of dealing with this issue not the way of avoiding dealing with it," he added.

Charles Kennedy told Blair that he had failed to justify his intended course of action.

"Despite all his persuasive efforts and that of the government every measure of public opinion does show that people are not persuaded as to the case for the course of action that is being followed," said the Lib Dem leader.

Blair also rejected repeated criticism of the "plagiarised" government document on Iraq.

The SNP's parliamentary leader, Alex Salmond, said the dossier amounted to "propaganda", pointing to alterations that had been made from the original dissertation on which it had been based.

Blair dismissed the criticism. "It is important that we give accurate information to people, and the information given was indeed accurate," he said.

The prime minister also said that he would "take full account" of anything Hans Blix reported to the security council on Friday.

"If Iraq is cooperating the inspectors can have as much time as they need," he said

"If Iraq is not cooperating then we have to be careful we do not get sucked back into the situation we had in the 1990s...the issue we come back to time and time again in order to avoid a conflict is will Saddam cooperate or not?"

Former Foreign Office minister Tony Lloyd questioned whether military action would make Britain less of a target for terrorists.

Blair denied the UK was "hell bent on war come what may".

Questioned about the motives of the growing anti-war lobby, the prime minister said the government "hold our views with as much convictions and sincerity as they hold theirs".

On a point of order Glenda Jackson had harsh words for the prime minister.

"I'm very proud of my party. It is my government of which I am ashamed," she said.

The Commons clashes came after a "heated" meeting of the Parliamentary Labour Party in which Jack Straw faced backbench anger over the government's policy.

Downing Street had earlier said that a broadcast in which Osama bin Laden calls on Iraqis to unite against the West appears to be genuine.

The recording, which the US says proves there is a link between al Qaeda and Iraq, calls for suicide attacks on the West.

Number 10 says the recording reveals a determination by bin Laden to "find common cause" on the principle that "my enemy's enemy is my friend".