Overweight, unfit and shy recruits are being given a second chance to join the British army via a four-week boot camp as the military seeks new ways to increase troop numbers in its under-strength armed forces.

The “soldier development course” – which first ran in September – is designed to help borderline recruits make the grade and is one of a range of measures aimed at stemming a 10% shortfall in fully trained personnel.

Speaking as the army unveiled its latest annual recruitment campaign, Col Nick Mackenzie, the head of army recruiting, said: “We are constantly looking at our publications and our policies to ensure we can get more people into the army.”

About 200 would-be recruits have already attended the boot camp, and the plan is to run nine such courses a year, taking in 50 applicants at a time, at a centre in Pirbright, Surrey.

Mackenzie said the course would help those with borderline fitness, who were “a bit slow on their run, or they were just a little bit too large”, to meet the minimum standard required.

The army is desperately trying to bolster soldier numbers after a long period of decline. There are 73,740 trained personnel, well below the target figure of 82,000.

In part, the military’s plan is to look at ways to ease the once strict entry requirements, recognising that young people are not as healthy as they once were as obesity rates have gradually risen across the population.

This year’s recruitment campaign is also aimed at teenagers and youngsters suffering from self-doubt and who are bombarded with superficial offers, from fake tans to makeup and from trainers to “Love Island-style” bodies.

“Confidence that lasts for a lifetime” can only be obtained from the army, claim the recruitment posters, which feature a range of images including a woman’s face in makeup and a pint of beer as examples of short-term alternative boosts to self-esteem.

Army recruiters say their research shows that 54% of 18- to 24-year-olds believe a lack of self-confidence holds them back, and the psychological issue is also one of those addressed on the development course.

Mackenzie said: “Some of those people go on the course because they are lacking a bit of confidence. It’s about bringing people on and nurturing them through the process. One part of it is about fitness, some of it is about confidence.”

Other measures introduced to ease recruitment this year include an end to the blanket ban on sufferers of asthma and eczema. “Whereas previously if you had had asthma that’s it, you are out, gone, now we need further medical evidence. We are bit more lenient to letting people come in,” Mackenzie said.

Blame for the shortfall has variously been placed on a lack of high-profile military missions for people to sign up for, a squeeze on soldiers’ pay, and problems with the Ministry of Defence’s contract with Capita, the company responsible for signing people up.

But last year’s recruitment campaign – aimed at “snowflakes”, “selfie addicts” and “phone zombies” – was deemed to have been a success, partly because it struck a chord among the target group of 16- to 24-year-olds.

The defence secretary, Ben Wallace, a former officer with the Scots Guards, said he hoped the 2020 recruitment campaign would build on last year’s: “I know from my own experience the confidence, self-belief and camaraderie a career in the armed forces can offer.”

The MoD said the 2019 campaign resulted in 90,000 applications to join the army between January and the end of November, achieving 90% of the annual recruitment target with three months of the financial year to go.

But that has not yet led to an increase in fully trained soldier numbers because of the time it takes to train them.