Some UK combat regiments are operating at almost 40% less than their required strength due to declining recruitment numbers, according to data.

Ministry of Defence (MoD) data shows numbers in Army infantry units have been consistently falling over the past five years, according to figures obtained by The Guardian under freedom of information (FOI) laws.

Information publicly published quarterly by the ministry noted a 7.6% drop in Army personnel on January 1.

But The Guardian’s analysis of the FOI figures shows nine of 16 infantry regiments were 20% below their required personnel level, four were 25% below and the prestigious Scots Guards unit was 37% below its target strength.

The infantry as a whole was operating at 17% less than its required level, the paper added.

Defence Secretary Ben Wallace has been urged to address the issue.

Shadow defence secretary Nia Griffith was quoted as saying the “shocking trend” had to be halted.

Ms Griffith said: “At a time when our country faces an increasing number of threats, it is simply unacceptable for numbers to be falling year after year.”

Tory MP Bob Seely criticised the firm Capita, which began managing recruitment for the MoD in 2012.

The MP for the Isle of Wight said: “I’m afraid to say that Capita have not been a success.

“If you talk to people who are wanting to go into the Army, the most common way they describe it is shambolic and chaotic.”

A Capita spokesperson said: “The partnership is in the middle of a well-publicised re-set, which started last year but is already seeing excellent results.

"This includes the busiest quarter since the partnership started seven years ago, with 1,000 more enlistments in January to March than the same three months last year; a successful trial to halve the amount of time to get recruits from application to basic training; and increasingly high proportions of applicants getting an offer of basic training, which is substantially better than pre-2012 [when Capita started the contract].”