Almost 18,000 British Army personnel are not medically fit to be deployed to all war zones leaving only 60,546 members that can be sent to the frontline.
With 22% of this force declared not fit enough to be sent to all war zones, there are fears that the army could be left dangerously undermanned.
The latest figures were revealed by the Ministry of Defence (MoD) in response to a written Parliamentary question tabled by the Conservative MP Andrew Bowie.
The British Army is supposed to have 82,000 troops but that has now fallen to just 78,407.
Mr Bowie, a former Royal Navy officer who uncovered the figures, said it is ‘appalling’ troop numbers have been allowed to get so low.
They also show that 7,890 Army personnel were ‘medically not deployable’ in April 2017, and another 9,971 were categorised as ‘medically limited deployable’ – meaning they can only be sent to some areas.
Mr Bowie, MP for West Aberdeenshire and Kincardine in Scotland, said: ‘The concern among Conservative MPs is that the Army is too small as it is, cutting it down to 82,000 was a mistake in the first place.’
“You are always going to have people who are medically unable to serve, but in the Armed Forces it is a serious worry that we have so many unable to serve as it drives down the level of our forces.”
An Army spokesman said: ‘The Army has enough people to perform its operational requirements to keep Britain safe.’