Political opponents, including former prime minister Sir John Major, have criticised the timing of Gordon Brown's latest Iraq announcement.

The prime minister, who on Tuesday was visiting Baghdad and Basra, said that 1,000 soldiers are to be withdrawn from the country.

They should be home before Christmas, Brown said. The move was interpreted as paving the way for an autumn general election.

But Sir John, who was prime minister during the first Iraq war, said Brown should have told MPs of the plans first.

"This is a statement that should properly have been made to Parliament," he said.

"I'm not sure what the mission of the remaining troops may be, but in particular I'm not sure what will happen between now and Christmas that will justify the thousand coming home."

Brown has repeatedly promised to make a statement on Iraq to the Commons, and is now expected to deliver one next week.

However it also emerged that the withdrawal of half of the 1,000 soldiers had already been announced.

Some 270 are thought to have arrived back in the UK already.

Shadow defence secretary Dr Liam Fox said: "A week ago Gordon Brown gave only around a minute of his 67 minute speech to the issues of Iraq, Afghanistan and our armed forces combined; but today he is happy to use our armed forces for a pre-election photo opportunity.

"Most people will see this cynicism for what it is. Our troops should not be used as a political football."

And he added that the "small print" revealed the "same old spin" from the government.

"Five hundred of these troops have already been announced earlier in the year and 270 are already back in the UK," Fox said.

"This is a cynical exploitation of our armed forces by a prime minister who puts the Labour Party's interests before the national interest."

And Liberal Democrat leader Sir Menzies Campbell said that while any troop withdrawal is welcome, Tuesday's move was "a cynical effort to manipulate the figures and make it look more significant than is really the case".

"In fact only 500 more troops will be pulled out of southern Iraq, since the withdrawal of the other 500 had already been announced," he said.

"It still leaves 4,500 British troops trapped in Basra airport where they no longer serve any real military or political purpose.

"What we need is a clear timetable to withdraw all our forces to safety within six months."