The case goes back to the 2003, when the Commission ordered EDF to repay a tax claim which the state had waived in order to boost the utility's balance sheet.

EDF initially won an appeal against the order in 2009 and 2012 court rulings, but the Commission issued a new order to repay the money in 2015. EDF repaid the amount that year, but then brought a challenge to the General Court of the European Union, the EU's second-highest court.

An EDF spokesman said the company had not yet decided whether to appeal again.

He said that since the money had already been reimbursed, Tuesday's ruling had no impact on EDF's accounts.

(Reporting by Philip Blenkinsop and Geert De Clercq; Editing by Robert-Jan Bartunek)