The Army's highest-profile combat unit is facing a manpower shortage even deeper than that of the Royal Regiment of Scotland.

Figures obtained by The Herald show that the Parachute Regiment's three battalions are 20% under-strength and struggling to retain their most experienced soldiers against the lure of better-paid mercenary jobs in Iraq.

As reported exclusively in The Herald yesterday, the RRS still has a shortfall of almost 15% in its frontline strength 18 months after its formation.

Even with the Paras' new glamour role of having one battalion permanently assigned to support the SAS, the regiment is 274 men below its "bayonet strength" of 1382.

The unit's first battalion - the group tasked from last year as back-up for special forces on covert missions - is 81 short, while the second and third battalions are respectively 103 and 90 men short.

All three battalions have traditionally attracted a disproportionate number of Scots since the regiment was created in the Second World War. During the Falklands conflict, its second battalion was known as "Jock Para" due to the level of Scots in its ranks.

Despite a Ministry of Defence statement that "validated" manning figures for the Army will be "unavailable until next April" because of problems with its new Joint Personnel Administration computer system, The Herald can also reveal that the Scots Guards are 72 soldiers short of their fighting strength of 612.

One company of the SG yesterday spearheaded a new Nato offensive into Taliban-held territory north of Gereshk in Helmand province. The Scots were asked to provide armoured infantry to support lightly-equipped Gurkhas.

A serving Parachute Regiment officer told The Herald: "A number of factors are responsible for the drop in manpower across the infantry. But it has little to do with recruiting. It's all about retention of the most experienced.

"The guys we really need to keep are being attracted into the private security sector by high pay. There is also a feeling that the Army is fighting two wars in Iraq and Afghanistan on a shoestring budget imposed by a government which doesn't understand or want to understand defence.

"Something's got to give. Why should guys risk their lives for 20-grand or less while their families are living in substandard military houses and they themselves are facing repeated tours of duty without proper breaks or training in between deployments?"

Brigadier Allan Alstead, a former commander of Scotland's 51st Highland Brigade, added: "Government policies towards the armed forces and the Scottish infantry regiments in particular have been a total and utter disaster, now reflected in falling manpower.

"The only answer is to restore individual regimental pride, improve pay, equipment and housing, and reduce overstretch."

Brigadier David Allfrey, the officer responsible for meeting the Army's manpower targets north of the border, dismissed the "tribal loyalty" argument as a cause for falling numbers.

"Only 8% of the young people interviewed by recruiters can even tell us who their local regiment is," he said.