The announcement that British troops are set to withdraw from Iraq has triggered further calls for an inquiry into the war.

The government has repeatedly cast aside demands for an inquiry with the reasoning it would be unhelpful while combat operations are ongoing.

"Now that Brown's fig leaf of a major British operation is set to disappear, he has no excuse to delay any longer on holding a full public inquiry into how this foreign policy catastrophe happened," said Liberal Democrat leader Nick Clegg.

All but several hundred of British troops are expected to have left Iraq by June next year, defence sources have confirmed.

Just 4,100 of the 45,000 soldiers that the UK sent to Iraq in the 2003 invasion remain in the country - the vast majority in the south around Basra.

"Our whole country will breathe a sigh of relief that an end to this illegal war is now in sight," Mr Clegg said.

According to officials speaking on condition of anonymity the withdrawal will begin next March, six years after the invasion.

A Ministry of Defence spokesman said: "We continue to negotiate our own future legal arrangements for the UK military role with the government of Iraq.

"Our negotiations have made good progress to date and we expect to be able to agree a sound legal framework with the government of Iraq before the end of the year."

About 300 troops are expected to remain in Basra to continue training and mentoring Iraqi security forces, with the rest being redeployed to Afghanistan.

The United Nations mandate for coalition troops in Iraq expires this year.

The US has committed itself to withdrawing troops from next year, with its military presence completely removed by the end of 2011.