The head of the army, General Sir Richard Dannatt, has called for it to be restructured to allow soldiers to spend more time with their families.
Dannatt said the nation's armed forces were being "seriously stretched" by the Iraq and Afghan conflicts and argued that the army should be expanded to 102,000 soldiers from the current 98,500.
Units should not be sent on operations for more than six months out of every 36, he added. At present, deployments are often only a year apart.
In a speech on Monday night, Dannatt said the restructuring would aim to offer British troops a more reasonable lifestyle.
The general also said he would reform the Army's fighting brigades into larger units that could be sent away less often.
"We have seriously stretched our soldiers -- both their goodwill and their families," he added.
Defence Secretary John Hutton, responding on BBC radio on Tuesday, agreed that maintaining troops levels in Afghanistan, where Britain has around 8,000 serving soldiers, was an arduous but necessary, task.
"The strain of mounting two major operations -- one in Iraq and one in Afghanistan -- is creating very substantial strain and stress on our military forces," he added.
British forces have been involved in heavy fighting in southern Afghanistan for many months, deepening public scepticism about the deployment. Another UK soldier was killed on Saturday, bringing the number of British troops killed there since 2001 to 142.
Opinion polls show that some two-thirds of Britons want British troops to be pulled out of Afghanistan this year.Reuse content