65-year-old military veterans face being mobilized under new powers to prepare the Armed Forces for war.
The Government is expected to increase the age at which the nation’s group of retired soldiers, known as the strategic reserve, can be called up from 55 to 65.
The new measures are being introduced as part of a new draft of the Armed Forces which will be published in Parliament later.
The changes will make it easier to mobilize tens of thousands of former military personnel.
The Army has shrunk to its smallest number in more than 200 years, with just over 70,000 full-time, fully trained troops ready to be sent to the front.
According to the existing rules, the group of retired soldiers can be called upon in case of “national danger, major emergency or attack in the United Kingdom”.
However, under the new changes this will be lowered to “war preparations”, which is already the limit for reservists who have recently left the Armed Forces.
The measures come amid fears that Britain could be dragged into a full-scale war with Russia within a matter of years.
Defense and security chiefs have repeatedly warned of the potential for full-scale war in recent months.
Al Carns, the minister of the Armed Forces, said shortly before Christmas that the war “is already knocking on the door of Europe” and that Great Britain had to be prepared for a conflict that was “bigger” than those fought in Iraq and Afghanistan.
Last week, the United Kingdom announced that it would be deploying troops to Ukraine, along with France, if and when a ceasefire agreement is reached between Moscow and Kiev.
While it is not clear exactly how many troops may be involved, reports have suggested that up to 7,500 UK personnel could be deployed.
If this figure is accurate, it would effectively mean that around 21,000 personnel would be committed to Ukraine – with a cohort deployed, another in training and a third recovering for operations there.
However, military analysts have warned that such a deployment would stretch the Armed Forces and effectively become an “all Army effort” to contain it.
Sources in the Ministry of Defense have pushed back against suggestions that 7,500 troops could be deployed, with insiders saying this could be lower.
On Friday, the Government promised to spend £200 million to upgrade armored vehicles and buy new kit in preparation for the peacekeeping mission.
The proposed changes will come into effect next year if approved by Parliament, the BBC reported.
The Government estimates that there are approximately 95,000 people within the strategic reserve, including veterans from the Royal Navy, the Army, and the RAF.
These are different for the reserve forces, which include personnel who volunteer part-time to serve in the military. There are currently almost 32,000 active reservists across the three wings of the Armed Forces.