Introducing fees for employment tribunals has been a "huge victory" for bad employers and has led to a collapse in the number of claims, a report by Britain's trade union body said.

The Trades Union Congress (TUC) said women and low-paid workers had been worst affected since the government brought in fees of up to £1,200 last year. The total number of claims had fallen by 79%, but there had been an 80% cut in sex discrimination claims, while cases of unpaid wages and holiday pay were down by 85%, a study found.

Frances O'Grady, the TUC general secretary, said: "Employment tribunal fees have been a huge victory for Britain's worst bosses. By charging up-front fees for harassment and abuse claims the government has made it easier for bad employers to get away with the most appalling behaviour. Tribunal fees are part of a wider campaign to get rid of workers' basic rights. The consequence has been to price low-paid and vulnerable people out of justice."

The justice minister Shailesh Vara said: "It is in everyone's interest to avoid drawn out disputes which emotionally damage workers and financially damage businesses. That's why we are encouraging quicker, simpler and free alternatives such as the early conciliation service provided by [conciliation service] Acas. It is not fair for the taxpayer to foot the entire £74m bill for people to escalate workplace disputes to a tribunal, and it is not unreasonable to expect people who can afford to do so to make a contribution. For those who cannot afford to pay, full fee waivers are available."