A Luxembourg court on Thursday overturned the verdict against a "Luxleaks" whistleblower who was convicted of leaking thousands of documents that revealed tax breaks for multinational firms.

Luxembourg's highest court rejected the conviction against former PricewaterhouseCoopers employee Antoine Deltour who in March had received a reduced six-month suspended jail sentence with a 1,500-euro fine.

The sentence against his colleague Raphael Halet, who received a 1,000-euro fine after an appeal, was upheld.

An appeal court will now hold a fresh trial with new judges, Luxembourg's highest court said in a statement.

The LuxLeaks scandal erupted in 2014 and sparked a major global push against generous deals handed to multinationals, which grew even stronger with new revelations such as the Panama Papers and Paradise Papers Leaks.

The blockbuster leak revealed the huge tax breaks that tiny EU nation Luxembourg offered international firms including Apple, IKEA and Pepsi, at a time when Jean-Claude Juncker, now head of the European Commission, was prime minister.