A documentary has claimed that many private security firms in the UK recruited soldiers from Africa to serve as mercenaries in Iraq, without confirming whether they were "child soldiers in the past". A former senior director at a British private security firm admitted that soldiers were preferred from Africa over Europeans, to save costs.

The documentary is titled, The Child Soldier's New Job, which shows around 2,500 former child soldiers from Africa's Sierra Leone recruited by British private security firm Aegis Defence Services to be sent to Iraq to work as mercenaries. Their employment contracts showed they were paid daily wages of $16 (£11). The documentary will air on 18 April in Denmark.

Aegis, chaired by Tory MP Sir Nicholas Soames, had entered into contracts worth several million-dollars to provide guards to protect US military bases in Iraq from 2004 onwards. The firm had been recruiting people from the UK, the US and Nepal, but later headed to African countries from 2011 onwards to save on costs. Canadian security company GardaWorld took over Aegis in 2015.

James Ellery, who was director of operations at the firm at the time of the Iraq contracts, told the Guardian that his firm had asked contractors to recruit people from countries such as Sierra Leone, "where there's high unemployment and a decent workforce", because they were affordable.

"You probably would have a better force if you recruited entirely from the Midlands of England. But it can't be afforded. So you go from the Midlands of England to Nepalese etc etc, Asians, and then at some point you say I'm afraid all we can afford now is Africans," the former brigadier in the British Army said. Ellery was an Aegis director between 2005 and 2015. He added that they never asked the recruits if they were soldiers in the past.

Mads Ellesøe, the film's maker said, "When war gets outsourced, then the companies try to find the cheapest soldiers globally. Turns out that those are former child soldiers from Sierra Leone. I think it is important that we in the West are aware of the consequences of the privatisation of war."

The documentary shows several interviews of former civil war fighters who now work in Iraq. Gibrilla Kuyateh, one of the interviewees said, "Every time I hold a weapon, it keeps reminding me of about the past. It brings back many memories." He goes on to add that rebels killed his mother and kidnapped him when he was 13. They taught him to amputate people's limbs and fire an AK-47.

The United Nations reportedly demobilised more than 75,000 fighters, including nearly 7,000 children, in the past that cost the organisation around $36.5m (£26m). However, the documentary claims that many private military firms have been recruiting mercenaries from poor countries like Sierra Leone, Uganda and Kenya.

Graham Binns, former CEO of Aegis and GardaWorld's senior managing director, disputed the claims and said, "We worked very closely with our audited, vetted and authorised agents to recruit, vet and screen our professionals. Our agents were authorised [as was the employment of individuals] by the relevant national government of the countries from which we recruited."