Campaigns against unpaid labour and the culture of endless internships have been gathering strength. But now there’s a new front: astonishingly, we find we’ve been paying companies with taxpayers’ money so they can exploit the young.

The fact that 5 per cent of apprentices surveyed by Department for Business, Innovation and Skills researchers were paid nothing at all is shocking: if the pattern holds with the broader population, it would imply 25,000 apprentices starting last year in a job with zero wages.

As Unionlearn notes, the situation has worsened since the government moved from weekly minimum wage to an hourly one. Both the survey of apprentices and advertisements for current apprenticeships show how employers are stretching the minimum wage by cutting nominal hours and demanding unpaid overtime. This is the dark side of employer calls for more “flexibility”, and it’s likely to increase with employer ownership of skills - now a Labour policy as well as a coalition one.

It requires the government more than ever to articulate a clear vision of what an apprenticeship is, so it can lay down rules that prevent abuse. The battle is already being lost: the most basic notion of an apprenticeship is that it is a paid job with training, but some employers do not pay and some do not train. Perhaps some do not do either.

The fact that potentially tens of thousands of young people would accept such a situation suggests that the public’s conception of an apprenticeship is fragile. People simply do not know enough to object if they are offered an apprenticeship without pay. What this means is that the strategy for exposing employers who flout the minimum wage falls down. HM Revenue and Customs relies on hotline calls from disgruntled employees. But if some are prepared to work and train for nothing, it’s unlikely that others will cry foul if they are paid below a minimum they may not know exists.

HMRC also supposedly pays attention to risk. Now we know that nearly half of hairdressing apprentices are paid below the minimum wage, surely they should be investigated as a matter of routine?

Training providers and colleges cannot evade their responsibility either: where employers are underpaying, providers must be turning a blind eye. This should stop. Educators and trainers are rightly concerned not just with transmitting prescribed knowledge and skills, but with the development of the whole person. Allowing them to be exploited is not acceptable.

The National Apprenticeship Service should at the very least monitor vacancies on its matching service. It’s an embarrassment for the government to be helping employers flout its own laws. Beyond that, the government should perhaps consider raising the minimum wage for apprentices significantly. If a business can’t afford more than #163;2.65 an hour, they probably can’t afford to provide long-term employment either.

In hairdressing, the worst low-pay offender, salon owners often hire apprentices, then let them go once their training period has elapsed, only to hire another cheap youngster. But in flooding the market with cheap labour, they also depress the value of their own skills. It’s an object lesson in false economy.

So it’s probably not a question of whether we can afford to scrap low-paid apprenticeships, but whether we can afford not to.