Dozens of soldiers who took part in heavy firefights in Afghanistan have suffered hearing problems and may never be able to return to the frontline.
Around 240 troops from the 1st Battalion of the Royal Anglian Regiment - known as the Vikings - underwent hearing tests and 35 have been referred to specialists.
The problems were caused by the soldiers' close proximity to high-velocity machine-guns, mortars and anti-tank weapons during a series of intense battles with the Taliban last summer.
Defence experts said loss of the experienced soldiers at a time when there is a chronic shortage of combat troops would exacerbate what is already a "crisis" in troop numbers.
Earlier this month, defence figures disclosed that almost one thousand servicemen have left the Armed Forces since the start of the year.
The figures followed a report by the Commons Defence Committee which said it was "deeply concerned" that the forces had been operating above their resources for seven of the past eight years.
Patrick Mercer, former shadow minister for security and an infantry commanding officer, said the Vikings were a "precious resource" that the Army could not afford to lose.
"This may only be 35 men but that's a platoon and a half and you have to look at whether this situation could be replicated when the Sherwood Foresters and the Grenadier Guards - who were in theatre at around the same time - undergo similar tests," he said.
The manning figures do not include the number of service personnel that are sick and injured, he said, and claimed the Ministry of Defence was "in denial" about the problem.
"The single most important piece of kit that we have got is the man that carries the pike, the man that pushes the bayonet, the man that throws the hand grenade," he said.
"The Armed Forces are in a parlous state in terms of those who do the fighting, the killing and the dying".
An MoD spokesmen said service personnel are issued with two forms of protective hearing equipment - ear plugs and ear defenders.
Many chose not to wear the equipment as they reduce awareness and the ability to hear commands, he added.
He said: "We are actively looking to acquire more advanced hearing protection equipment that is based on active noise reduction technology, can be worn with standard helmets and is compatible with personal role radio but minimises the blocking out of other noise such as voices."
