The United Kingdom is to confirm the deployment of a further 1000 troops to Afghanistan on Monday in response to a direct appeal from Nato's Supreme Allied Commander (Saceur).

Des Browne, the Defence Secretary, is understood to be furious that details of the deployment were leaked, but is convinced more troops are needed to deal with an expected spring offensive by the Taliban in the Helmand region.

Last night, Mr Browne confirmed that Britain was bolstering its force in the country, saying a decision to send in extra UK troops to Helmand had been taken after efforts to get more help from partners such as France and Germany failed.

The government had been expected to announce the deployment of 1000 extra troops on Monday, but Mr Browne said he felt "obliged to clarify the situation" earlier after widespread speculation.

The matter was discussed in Cabinet yesterday, and the "final details" of the force levels are now being drawn up by the MoD.

There are already 5600 British troops in Afghanistan and the government has been reluctant to send further soldiers but now that 1600 troops are returning from Iraq it has more flexibility.

Liam Fox, Shadow Defence Secretary, condemned the government's failure to persuade Nato allies to send in their troops, and said the timing of the move revealed that British forces were too overstretched to carry out duties in Iraq and Afghanistan. "We have now had three reinforcements since the time that (then Defence Secretary) John Reid told us we were not going to be under-deployed in Afghanistan," he said. "It is clear that the government has failed to get our Nato allies to carry their share of the burden in Afghanistan.

"Too many of our European partners are pocketing the Nato security guarantee but leaving UK taxpayers and the UK military to carry the cost."

Nick Harvey, LibDem defence spokesman, said: "Attempts to bolster our efforts in Afghanistan are to be welcomed, but the fact remains that the British Army is severely overstretched.

"Any hope of maintaining our commitments to Afghanistan relies on us being able to get our troops out of Iraq. There must be clear objectives and clear aims, rather than the confusion that has surrounded much of the mission.

"It is vital that pressure is kept up on other Nato countries to ensure that they pull their weight. Failure would be disastrous both for Afghan-istan and the alliance."

Earlier this week the Prime Minister announced that the British force in Iraq was to be reduced by 1600 troops, easing the pressure on the Army.

Last night one senior officer privately described Afghani-stan as a Cinderella operation, compared with Iraq.

Nato has some 35,000 troops in the country. There is frustration that the brunt of the fighting in Helmand has been borne by troops from Britain, the US and Canada. There has been particular criticism of France and Germany whose troops are deployed in the more peaceful areas of the country.

It is understood that the force package to be announced on Monday will include two squadrons from the Household Cavalry, with around 230 troops. The regiment is also sending two squadrons - including Prince Harry's A Squadron - to Iraq.