Some firms have developed scams to avoid paying the national minimum wage, including charging for uniforms, clocking off cafe workers when there are no customers, and mis-using interns, according to a new report.

A study by the TUC found that apprentices were most likely to be underpaid, with suggestions that 120,000 were not receiving the proper rate.

Despite improvements to enforcing the statutory rate, new ways of cheating have emerged, said the union organisation.

The research found that a minority of employers were under-recording workers’ hours, not paying for travel between work sites, or “vanishing” to avoid paying fines, only to reappear under a different name.

The TUC called for enforcement of the minimum wage to be improved to combat rogue employers.

TUC general secretary Frances O’Grady said: “Failing to pay the minimum wage is an antisocial act that squeezes those workers who have the least. There should be no hiding place for cheapskate bosses who try to cheat their workers out of the minimum wage.

“We must engage in a constant battle to ensure that every worker gets at least the minimum. It is clear that some employers are actively looking for new ways not to pay even the legal minimum.

“There should be a broad consensus between political parties, good employers and trade unions that the minimum wage must always be enforced effectively. We urge everyone to support the TUC’s plan for ensuring continuous improvement to the minimum wage system.”

The TUC called for more enforcement officers to be hired, naming and shaming of all non-payers, and an increase in the maximum fine from £5,000 to £75,000.

Other groups at risk of not being paid the proper rate include migrants, domestic workers, interns and temporary agency staff, said the report.

A Business Department spokesman said: “It is not only unacceptable to pay less than the minimum wage, it is against the law.

“We’ve taken tough action to crack down on offenders by naming, shaming and fining them as well as helping workers recover the hundreds of thousands of pounds in pay owed to them. We are also looking at what more we can do to make sure they are paid fairly in the first place.”