The shortfall in military personnel is the largest it has been in a decade and ministers must take swift action to close the gap, the official Government watchdog has said.
The National Audit Office said the Ministry of Defence was some 8,200 full-time regulars below its existing requirement, with “much larger” gaps in more than 100 critical skills.
It urged ministers to “fundamentally change” their approach to training and recruiting personnel, to ensure the military can keep up with “modern world threats”.
The verdict is a humiliation for ministers, who for months resisted calls to boost troop numbers only to eventually concede to a review.
The NAO said the number of regulars was 5.7% below the existing requirement, with a number of specific services unable to carry out operational tasks without cancelling leave or training.
It said the challenge was “likely to grow” as the MoD will require specialist digital skills to ensure it can continue to respond as warfare moves increasingly into the technological age.
And it said the Government was unlikely to close the gap in the next five years.
Shortfalls are borne primarily from recruitment and retention problems, with sign-ups of regulars in 2016/17 down 24% on targets, while the number leaving has increased from 3.8% a year in 2010 to 5.6% last year.
Meanwhile, official surveys show satisfaction with pay, accommodation and service life had by last year dropped to record lows among personnel.