The Royal Regiment of Scotland is 331 soldiers short of its front-line fighting strength on the eve of the latest deployment to Afghanistan, the Herald can reveal.

Two of its five regular battalions and an armoured company have been earmarked for the action against the Taliban.

These three units are the worst-manned in the regiment, with a collective shortfall of 277 trained men among them.

The RRS, formed in 2006 from the controversial merger of six historic infantry regiments, has 2611 officers and men in its ranks when it should have 2942.

The Highlanders (4th battalion, RRS) are the worst affected with a shortfall of 102, the equivalent of an entire rifle company. It is also the unit tasked to provide a reinforced Warrior group of about 150 to give extra firepower and armoured protection to the troops fighting in Helmand.

The Argylls (5RRS) and the Royal Highland Fusiliers (2RRS), the two battalions earmarked for combat, are collectively 175 soldiers below complement and will have to take drafts from other units to make up their numbers before flying out.

As reported exclusively by the Herald last week, more than 1800 Scots in total are to be sent to Afghanistan to add muscle to 16 Air Assault Brigade when it takes responsibility for the embattled southern province next month.

Apart from infantry, the tanks and light reconnaissance squadrons of the Scots Dragoon Guards are also to deploy over the next few weeks to prepare for a pivotal spring offensive against the Taliban.

An official announcement of the composition of the force, due to take over from Edinburgh-based 52nd Brigade at Lashkar Gah, will be made in Parliament this week.

The Argylls have been trained as a specialised helicopter assault force for the mission and are already part of 16 AA Brigade along with two battalions of the Parachute Regiment.

A Ministry of Defence spokesman said: "The RRS is about 11% below its bayonet strength, in common with most of the Army's infantry. But there are a sizeable number of recruits in the training pipeline.

"It should also be remembered that more than 350 Scots soldiers who would otherwise be in the regiment are not counted because they are in training posts or on courses."

However, that would effectively be cancelled out if more than 200 mainly Fijian Commonwealth and 55 non-Commonwealth volunteers serving in Scotland's infantry were taken out of the equation.