Brussels says a court decision handing Apple victory last year in a big tax case was “contradictory" and committed legal errors, in a filing for its appeal released on Monday.

The EU is pushing back against the ruling by the bloc's general court in the €13 billion tax case. The court rejected arguments by the European Commission that Apple had to cough up because it struck an illegal tax deal with Ireland.

It was a bitter defeat for the EU's competition commissioner, Margrethe Vestager, who has been leading efforts to rein in multinationals’ ability to strike special tax deals with individual EU countries that she says amount to illegal state subsidies.

In an online summary of the appeal posted online, the EU said the court's decision “constitutes contradictory reasoning,” saying it misinterpreted the lack of staff at Apple's two Irish units to represent the level of technology licensing attributed to them.

The court also “committed several errors of law” when it decided the EU Commission failed to prove that Apple gained an advantage, it said.

The EU is appealing the case to the European Court of Justice.