Halfords has been criticised for running a government-backed traineeship first exposed by UniteLive that sees young jobseekers work for two months without pay.
Financial services firm Prudential has also faced condemnation for taking part in the “profit boosting” schemes.
Some smaller companies, along with training providers, are running unpaid traineeships that last six months.
Traineeships, introduced in 2013, are facing scrutiny as JobCentres gear up to potentially sanction thousands of young benefit claimants if they don’t agree to take one.
Halfords and Prudential, in conjunction with a training provider, run traineeships for 16- to 24-year-olds that mix unpaid work with classroom based lessons in Maths, English and skills such as teamwork, CV writing and IT.
The schemes – consisting of 25 hours of work a week in Halfords for two months and six weeks of work at Prudential – are unpaid with participants claiming benefits to support themselves.
Most participants are not offered a job or apprenticeship once their traineeship ends.
Joe Crossley, business development manager at Qube, which provides the training for the Halford’s scheme, said preparing participants for work within six weeks was a short time frame.
He told the Guardian, “They don’t know how to present themselves or how to dress or not to use their mobile phone. They have to develop those skills and (to do so) in six weeks can be a challenge.”
Glasgow University research fellow and benefit sanctions expert, David Webster, said using financial threats to make people undertake unpaid work leads to abuse and poor training and does little to tackle unemployment.
He said, “Because referrals are made under threat of sanction, the JobCentre doesn’t bother to make these things suitable or realistic.
“People end up just being abused, really. Only if activities are voluntary can you be clear that they have value to the participant.”
Unite assistant general secretary Gail Cartmail said traineeships were about free labour.
She said, “These schemes are clearly not about training, but forcing people into unpaid work. The fact that well-known brands are operating these schemes to boost their profits is especially alarming.
“These schemes are a worst-case scenario and fall far short of the assurances Unite was given when these traineeships were introduced.”