Bronwyn McKenna, UNISON's assistant general secretary, said: "The Supreme Court correctly criticised the government's failure when it set the fees to consider the public benefits flowing from the enforcement of legal rights enacted by Parliament".
Official statistics show that the number of cases taken by workers has dropped by almost 70% since the fees were introduced, with TUC research showing the fall was especially high in cases involving part-time work rules (-83%), sexual orientation discrimination (-75%), and unauthorised deductions from wages (-78%).
The aims of the introduction of tribunal fees was to pass some of the cost of the tribunal system from the taxpayer to people making claims, and to reduce the number of "nuisance" claims being brought by opportunist workers hoping for a settlement.
The Supreme Court also held that fees indirectly discriminated against women, who were more likely than men to suffer discrimination at work.
Mr Burgon, whose party had vowed to abolish the fees during the general election, continued: "It's an important day for access to justice for ordinary working people everywhere".
Tribunal fees were introduced in July.
For workers with relatively low value claims for the likes of unlawful deductions from wages or holiday pay, the fees were a significant impediment.
"Many claims which can be brought in [employment tribunals] do not seek any financial award: for example, claims to enforce the right to regular work breaks or to written particulars of employment", he said.
The Law Society of England and Wales president Joe Egan said in a statement the decision was 'a triumph for access to justice, and a resounding blow against attempts to treat justice as a commodity rather than the right it is.' It argued 'against the hike in tribunal fees before it was implemented and - like so many others - warned that they would deny people the chance to uphold their basic rights at work.
This dates back to July 2013, when the fees were introduced by the then Lord Chancellor Chris Grayling. The government may be facing claims for a refund from thousands of claimants who have paid fees. Fees start at around £160, and increase to between £230 and £950 for further hearings.
Largely the arguments at the Supreme Court centred on whether or not the fees regime could be objectively justified.
"There is ... no dispute that the purposes which underlay the making of the fees order are legitimate", said Lord Reed, giving the judgment of the court. Since it had that effect as soon as it was made, it was therefore unlawful and must be quashed. The Government must scrap them in light of the Supreme Court's judgement. He added: "This ruling is a victory for access to justice and common sense - workers' rights are not worth the paper they are printed on if they can not be enforced". At the same time, the government had not considered "the public benefits" of enabling individuals to enforce their domestic and European Union employment rights via tribunals, he said.