Government plans to send an increasing number of Army reservists to war should be urgently re-examined, according to a group of senior Army commanders and academics who say just one in 20 Territorial Army soldiers is adequately trained to serve on the front line.
In a letter to The Daily Telegraph, the coalition of military experts said they supported plans to expand and increase investment in the nation's reserve forces.
But they argued any widening of their role should not be at the expense of regular soldiers.
The letter, whose signatories include Dr Peter Caddick-Adams, a serving TA officer and defence analyst, Col Tim Collins, a former SAS commander, and Col Richard Kemp, a former Afghanistan commander, said: "The Government's intention is for Britain to rely increasingly on the Territorial Army and other reservists to plug the gaps in the nation's defence. Indeed, the reserve forces are to be expanded and investment made in order to raise the skill levels and capabilities of reservists.
"We welcome this commitment to the strengthening of the TA. However, any further widening of the role of the TA should not be at the expense of the regulars, and cannot be seen as a substitute for an adequately resourced regular Army."
The letter said front-line operations required "a level of fitness, experience, and training to regular Army standards that cannot readily be matched by part-time soldiers," and that around 1,500 personnel - 5% of TA soldiers - had the sufficient training to be deployed in the way the Government envisages.
Thousands of British servicemen and women are facing redundancy as the Government seeks to cuts its defence budget in measures set out under the Strategic Defence and Security Review.
According to the group of six senior commanders and analysis, the Army will soon be smaller than at any time since the late 19th century and will have lost a fifth of its strength by the end of the decade if cuts continue at the same rate.
They called on the Ministry of Defence to stop further cuts in Army manpower and review the current redundancy programme.
"The Government should re-examine this aspect of the Strategic Defence and Security Review and recognise that the primary role of the TA and other reserve forces is as a vital support to the full-time professionals, not as an alternative to them," the signatories added.