PARIS, May 6 (Reuters) - France's highest administrative court upheld on Friday an earlier state decision that had increased the amount of electricity which power group EDF was forced to sell to rivals at below-market prices.

The French government, which owns over 80% of EDF, took the decision earlier this year amid rising energy costs and ahead of the presidential elections, won by Emmanuel Macron, in April.

The Conseil d'Etat said in a statement that this was a "public interest" measure and it had therefore rejected a demand from EDF trade unions to suspend it. Unions had argued the measure was financially-crippling for the company.

(Reporting by Dominique Vidalon; Editing by Sudip Kar-Gupta)