Lawyers for Karim Benzema urged a top French appeals court on Monday to throw out a years-long case over an alleged attempt to blackmail Mathieu Valbuena over a sex tape, which has kept the Real Madrid star from playing for France's national side.

The French striker argues that a police officer used dishonest methods to draw him into the affair, which began in June 2015.

That was when Valbuena received a call from a blackmailer who threatened to release an intimate video, and contacted the police.

Investigators later accused Benzema of acting as an intermediary between the presumed blackmailers and Valbuena, which Benzema has denied.

While resorting to ruses can be common in police work, "the sin is in the zeal shown by this officer", Benzema's lawyer Fabrice Spinosi told the Court of Cassation in Paris.

"He eventually took charge of the exchanges by regularly renewing his contacts" despite Benzema's attempts to end their conversations, he said.

A previous appeal to a court in Versailles in December 2016 had failed, but the Court of Cassation later annulled that ruling and instructed the Paris Court of Appeal to hear the case again.

Benzema has been under formal investigation while fighting the charges and has not played for France since 2015.

The Cassation court said Monday that it would issue its decision on December 9.

If Benzema's claim is rejected, the prospect of a trial will loom, whereas acceptance would likely result in the charges being dropped.