Ms Liddell said the UK would consider attacking Iraq without UN support if one state tried to block international action "for its own purposes".

Her comments to BBC Radio Scotland came as the prime minister warned against any display of weakness in the UK's position on Iraq and his attempt to win over doubters amongst his own backbench MPs.

If we do not disarm Saddam of weapons of mass destruction those weapons will find their way into the hands of terrorists and we in this country could be at threat. Helen Liddell

Ms Liddell insisted there were no splits in the UK Cabinet despite growing concerns among some Labour MPs.

She said: "Our preference throughout, and indeed I support this whole-heartedly, is to go down the UK route.

"But if we do go back and one state, for its own purposes, tries to block that action by the United Nations, then I believe we still have to proceed to disarm Saddam."

She added: "There is little doubt in my mind that if we do not disarm Saddam of weapons of mass destruction those weapons will find their way into the hands of terrorists and we in this country could be at threat."

Meanwhile, Tony Blair was accused of being too scared of Labour backbench opposition to his policy on Iraq to have a full-scale Commons debate on the crisis.

The Scottish National Party Westminster leader Alex Salmond compared "meaningless" discussion of Iraq policy in the Commons with Thursday's planned debate on the issue at Holyrood.

The SNP motion accuses Tony Blair of pursuing "an inevitable path to war".

Mr Salmond said: "The Scots Parliament is pursuing proper democracy, not the hypocrisy of Westminster.

"While Westminster is to have another meaningless and inconclusive adjournment debate on the Iraq crisis, the Scottish Parliament is having a real debate based on a real motion from the SNP."

Tam Dalyell, Labour MP for Linlithgow and Father of the House of Commons, said: "It is ironic that the Scottish Parliament can find the means of having a meaningful debate on Iraq, while the Commons is refused."

Ms Liddell said she would take MSPs views to the Westminster Cabinet if they expressed opposition to war during the debate on Thursday.