Changing the employment tribunal system could give a green light to rogue bosses to break the law, union leaders have warned.
The TUC said it is concerned that calls from business groups for an increase in the qualifying period in which workers can claim unfair dismissal, from one to two years, would allow firms to sack staff on a "whim".
The Government is expected to launch a consultation on the future of employment tribunals in the wake of complaints from business groups about a 56% increase in cases last year.
A fee or deposit, returnable if the claimant wins the case, is expected to be among the main options, with proposals likely to range from £30 to £500 per case in a bid to discourage spurious claims. The TUC said that making people pay a fee of up to £500 before they can go to a tribunal would deter many employees with genuine cases, especially low-paid workers who have just lost their jobs.
General Secretary Brendan Barber said: "At the heart of any change to the tribunal system has to be the desire to make it more effective at delivering justice to the thousands of people who every year are wronged at work.
"While employer groups complain that tribunals are costing them too much, they seem to have lost sight of the fact that if firms treated their staff as they are meant to, few would ever find themselves taken to court.
"Instead of a focus on the employment tribunal process, ministers' time would be better spent looking at why so many companies, especially small employers, have such poor employment practices.
"When things go wrong at work, it's better for everyone concerned that the problem is resolved within the workplace, which is why mediation and the assistance provided by unions and Acas is so invaluable.
"The Government should stand firm in the face of the intense employer lobbying seen in recent weeks and leave employment tribunals to continue holding rogue employers to account and delivering justice for all workers who have been discriminated against or treated unfairly."
The British Chambers of Commerce said employment tribunals were in "dire need" of reform, claiming they were too slow and weighted in favour of workers.