The number of employment tribunal cases has plummeted 59% in the last year, figures from the Ministry of Justice (MOJ) have shown.
There were 5,619 cases between January and March this year compared with 13,739 in the same period in 2013.
Officials said the dramatic reduction was partly explained by the resolution of several class action cases brought on behalf of airline cabin crew.
But unions said new fees had put workers off taking employers to court.
Fees of up to £250 to begin proceedings at an Employment Tribunal were introduced on 29 July 20113. There are further fees as cases progress.
TUC general secretary Frances O'Grady said: "If an employer breaks the law and sacks someone unfairly, sexually harasses them or cheats them out of their wages, it's understandable that an individual should want to seek some kind of redress.
"In the past there were no fees, and workers who felt they'd been wronged could have their case heard and the tribunal would either find for them or in their employer's favour.
"But last summer, the government decided to restrict justice to those who could afford to pay a fee."
Ms O'Grady said low-paid workers trying to claw back wages they were owed by their bosses were being put off making a claim, often because the cost of going to a tribunal was more than the sum of their outstanding wages.
"The huge drop in cases taken certainly doesn't mean that Britain's bosses have got a whole lot nicer in the past year," Ms O'Grady added.
"It's simply because pursuing a complaint against a bad employer has become too expensive for many workers, and that is just plain wrong."
But 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 cheaper alternatives like mediation and arbitration.
"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.
"As for those who cannot afford to pay, fee waivers are available."
The figures showed an 85% fall in the number of claims for unpaid wages, a 62% drop in unfair dismissal cases, while sex discrimination cases were down from 6,017 to 1,222.
Dave Prentis, general secretary of Unison, said: "Today's figures make shocking reading because individual claims are now at a perilously low level.
"While Unison and other unions continue to lodge claims on behalf of groups of members, it is clear that the introduction of fees is undermining the whole tribunal system.
"The government's motive in imposing these hefty fees was to make it as difficult as possible for workers to seek justice and fuel a hire and fire culture for unscrupulous employers."
Unison lost a High Court challenge over the introduction of fees and has lodged an appeal, saying that today's statistics added "significant weight" to the union's arguments that workers were being "priced out of justice."