The inflation-linked increases were agreed as part of a three-year wage deal struck in 2018 and were due to come into force in April 2020.

But the government did not pay them, saying they were unaffordable amid the economic devastation caused by the COVID-19 pandemic.

The Labour Appeal Court said last month it would be unlawful for trade unions to enforce the wage increases because it would contravene parts of the constitution and public service regulations.

The judgment was a major victory for the government, since public finances have been hugely stretched by the pandemic.

The PSA trade union, which represents some 240,000 public sector employees, said it would file papers at the constitutional court late this month. "The state must be held accountable for signing an agreement that it had no intention of implementing," it said in a statement.

(Reporting by Alexander Winning; Editing by Nqobile Dludla and Mark Potter)