Gordon Brown today cleared the way for British troop numbers in Iraq to be reduced by 2009, claiming that the Army will continue to hand over further duties to the Iraqis.

The Prime Minister told the Commons that the general training and mentoring of Iraqi combat troops in 14th Division should be completed around the turn of the year, leaving them fit to take over a number of British responsibilities.

At the same time, he said Iraqis should be able to take over control of Basra Airport, where the remaining British force is based, by the end of this year.

"As we complete these tasks - and as progress continues across these different areas - we will continue to reduce the number of British troops in Iraq," he said.

Mr Brown said that he expected to see a "fundamental change of mission" in the first months of next year as Britain moved to a more normal bilateral relationship with Iraq.

David Cameron, however, suggested that since Mr Brown’s promise to reduce troop numbers last October the number of British soldiers in Iraq has increased.

He told MPs: “The Prime Minister said last October, and I quote, ‘We plan from next spring to reduce force numbers in southern Iraq to a figure of 2,500’.

“Yet currently, for good reason, there are over 4,000 servicemen and women stationed in Iraq.”

Mr Cameron said that if you included service personnel serving at sea the figure was more than 6,000.

He asked Mr Brown to clarify “what a combination of written answers and the MoD website suggest - that the figure has actually increased since October”.

The Conservative Party leader said: “These are not abstract numbers, these are not abstract announcements, these are people with families and responsibilities who are already coping with the consequence of overstretch and they deserve the very best treatment, not spinning over numbers and announcements.”

He was responding to the Prime Minister, who had claimed that the security situation in Basra had been "transformed" since Nouri Maliki, the Iraqi prime minister, launched Operation Charge of the Knights against the militias in the city last March.

As a result, it was now hoped that local government elections could be held before the end of the year while the Basra Development Commission, co-chaired by British businessman Michael Wareing, was due to present its plan for economic reconstruction in the autumn.

Once the combat training of the Iraqi 14th Division was completed, Mr Brown said that British troops would move on the specific tasks of mentoring the headquarters and other specialist tasks.

With 4,100 British troops still in Iraq, Mr Brown acknowledged that the reduction in force levels had not been as rapid as had been previously planned. He said a decision had been taken to "pause" the drawdown of troops so they could support the Iraqi operation Charge of the Knights.

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