The Defence Secretary today announced the abandonment of a planned withdrawal of 1,500 British troops from Iraq amid a dramatic upsurge in violence in the southern city of Basra.

Des Browne announced that the Prime Minister's pledge, made last October, of bringing the troops home would not be fulfilled because the Iraqi Army required surveillance and logistical support to bring Shia militia affiliated to the radical cleric Moqtada al-Sadr under control.

He added, however, that even before last week's escalation in fighting, military assessments had concluded that Mr Brown's pledge was untenable and that planned redeployments would have to be slowed down.

The Conservatives responded by accusing the Prime Minister of "playing party politics" with Iraq by making predictions last autumn that he could not keep, a claim fiercely denied by Mr Browne.

"Before the events of the last week, the emerging military advice - based on our assessment of current conditions then - was that further reductions might not be possible at the rate envisaged in the October announcement, although it remains our clear direction of travel and our plan," the Defence Secretary told the Commons.

"In the light of the last week’s events, however, it is prudent that we pause any further reductions while the current situation is unfolding.

"It is absolutely right that military commanders review plans when conditions on the ground change, so at this stage we intend to keep our forces at their current levels of around 4,000 as we work with our coalition partners and with the Iraqis to assess future requirements. I would expect to be able to update the House on force levels later this month."

Today's announcement marks a setback for British troops in Iraq and the Prime Minister's strategy of slowly drawing them down after training their Iraqi replacements.

Last autumn, in a move which appeared to contradict the United States "surge" strategy of introducing more troops to Iraq to quell unrest, the British military pulled its troops out of Basra palace to the airport on the outskirts of the city.

The soldiers stationed there now no longer play a direct role in Basra but instead provide logistical, air and surveillance support for the newly-trained Iraqi Army.

However, last Tuesday, Iraqi forces became embroiled in battles against the Shia militiamen affiliated to the Mahdi Army, leading to concern that violence in Basra would escalate out of control.

Liam Fox, the Conservative Shadow Defence Secretary, claimed that the Prime Minister had been guilty of trying to boost popularity and playing politics in his October statement predicting withdrawals.

"I hope that the Government has now realised the need not to play party politics with troop numbers," he said. Of the soldiers serving in Iraq, he added: "They are willing to make the sacrifice, they just expect the truth."

Mr Browne retorted that party politics had played no part in the Prime Minister's troop withdrawal pledge.

"Great care was taken in the information that was given to the house in October by the Prime Minister that that information and that plan reflected the latest military advice," he said. "There is no question of anyone using troop numbers for party-political purposes."

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