Chelsea goalkeeper Thibaut Courtois and his father, Thierry, said they will initiate legal proceedings against former Belgium coach Marc Wilmots after he repeated claims the two leaked sensitive team information during Euro 2016.

Wilmots told beIN SPORTS that his lineup could be seen on social media before it had been published prior to matches, meaning "a player has sold out the national team."

The coach, who left his position after failing to lead Belgium past the quarterfinal stage of the 2014 World Cup and Euro 2016, said "several French journalists said they had proof it was Courtois' dad who did that."

Courtois, who openly criticised Wilmots' tactical choices following Belgium's quarterfinal loss to Wales in France two years ago, responded on Facebook.

"Monsieur M. Wilmots, who is not doing this for the first time, has reiterated publicly and gratuitously accusations that tarnish my honour and reputation, as well as those of my father," he wrote in French and Dutch.

"Together, we have decided to made an official criminal complaint for slander and defamation."

Thierry Courtois told Het Nieuwsblad that Wilmots needed to back up his claims.

"It's a very serious accusation and I know who has been circulating it," Thierry Courtois said. "I don't understand. I was a high-level athlete, coach and sporting director myself. If you work together towards a goal, there can be no leak. So it's nonsense. It's a load of rubbish. If he says he has proof, he should show it."