Unison has secured a hearing in October for a potential Judicial Review of the introduction of up-front fees to be paid by employees wishing to take their employers to an employment tribunal.
It follows today's introduction of employment tribunal fees to be paid by claimants in cases at the employment tribunal and the Employment Appeal Tribunal.
General secretary of Unison, Dave Prentis, said: "The timing could not be more critical, but today we are one step closer to justice for workers.
"The Government should not put a price on justice," he added. "It is disappointing that in the interim fees will still be paid, but we will be making a strong case for a Judicial Review in October because we believe that these fees are unfair and should be dropped."
Unison had previously had its call for a Judicial Review rejected.
There are two levels of fee, reflecting the expected complexity of the case. For level 1 claims, which include claims for unpaid wages, holiday pay and redundancy payments, the issue fee will be £160 with a hearing fee of £230. For level 2 claims, relating to unfair dismissal, discrimination and equal pay, the issue fee is £250 and the hearing fee will be £950.