A Nato official suggested yesterday Britain may increase its military commitment in southern Afghanistan in spring to provide the mobile combat reserve for a decisive push against Taliban insurgents.

The Herald revealed earlier this month that up to 1400 Scots soldiers will be fighting in Helmand province alongside 1500 paratroopers and several hundred special forces as the spearhead of an 8000-strong British deployment.

The surge will involve more than half of the Royal Regiment of Scotland's soldiers (RRS) and all three battalions of the Parachute Regiment - in the biggest ground offensive since the allied invasion six years ago. Two battalions out of five regular units in the RRS - the Royal Highland Fusiliers (RHF) and the Argylls - and a reinforced armoured infantry company from the Highlanders are on stand-by or training for a March deployment.

Nato spokesman James Apparuthai said yesterday he understood the UK was talking about reinforcing its planned 7700-strong garrison.

Speaking on behalf of Jaap de Hoop Scheffer, Nato's secretary-general, he said: "The British in the south are talking not only about keeping what they have, but potentially increasing it." Nato sources later backtracked on his remark, stressing that he was not expecting any offer of additional UK troops and was simply seeking to reflect the solid nature of Britain's commitment to the International Security Assistance Force.

The Ministry of Defence also said there were no plans to send more British troops to Afghanistan.

However, at an alliance summit in the Netherlands later this week, the Nato secretary-general is expected to issue another appeal to member states for more troops and helicopters.

Any suggestion Britain should increase its commitment in Helmand, where troops have been engaged in fierce fighting with Taliban militias, would be controversial. Politicians of all parties have long said that the UK is bearing too much of the burden in Afghanistan and urged Nato allies to do more.

Liberal Democrat defence spokesman Nick Harvey said yesterday: "Our armed forces are already suffering because of too many commitments. If we take on a bigger deployment in Afghanistan then all the current problems of overstretch will only worsen. All the potential benefits of a withdrawal from Iraq will be undone if we take on a bigger role in Afghanistan."

Afghan president Hamid Karzai is expected to hold talks with Prime Minister Gordon Brown on the future of Britain's commitment to Afghanistan during a visit to the UK over the course of the coming week.

Mr Appathurai detailed the gaps which currently exist in the Nato deployment. He told the BBC: "From a Nato point of view, 90%-95% of what we want is on the ground, but we need more helicopters, we need more transport aircraft and we need more manoeuvre capabilities.

"Most of all, we would like more trainers from the Nato nations. In the end, the Afghans are going to have to fight their own fight and the way that happens is if we help train and equip them."

Mr Appathurai also indicated Mr de Hoop Scheffer would welcome the appointment of a senior political figure to co-ordinate the international community's civilian reconstruction and development work in the country.