Statistics from the Ministry of Defence show there has been an increase in the number of recruits under the age of 18. In the past two years the army's intake aged 16 and 17 increased from 22.5 per cent to 24.1 per cent.
Ellis Brooks from Quakers in Britain told Premier's News Hour: "These figures are so disappointing. It's devaluing the lives and choices of young people and it's actually normalising war. It's making war more likely for the future."
The Ministry of Defence told Premier that no one is forced to sign up and many young people choose to do so because of the skills and discipline training offers.
A spokeswoman added that teenage recruits will not face a combat role until the age of 18 and will be offered the chance to sit GCSEs and other exams.
But Brooks said we were "failing as a society if the only choice that we're offering is a career in the armed forces".
He added: "We're not talking about any old job. We're talking about a job where you are asked to participate in killing".
The UK is the only permanent member of the UN Security Council that still recruits 16 year olds.
Anyone under the age of 18 who applies to join the armed forces must have parental consent.
