A decision on whether the blackmail case involving former France teammates Mathieu Valbuena and Karim Benzema will be dropped is to be made early next month, a court in Paris ruled on Thursday.

Real Madrid forward Benzema is one of six men facing charges linked to the alleged attempted extortion of Fenerbahce midfielder Valbuena over a sex tape.

The Paris Court of Appeal ruled on Monday that the work of undercover policeman Yann Bessette, known to the alleged perpetrators as 'Lukas,' and his alleged incitement of them to commit an offence, could lead to the case collapsing, L'Equipe reported.

After two hours of arguments from counsel behind closed doors, the court said it would make its decision public on Nov. 8.

The case dates back to 2015, when Benzema was among those charged by police.

It was suggested that Benzema, who faces preliminary charges of conspiracy to blackmail, acted as an intermediary between Valbuena and the other defendants, some of whom are close to him.

The 30-year-old has always maintained his innocence, and last year the Court of Cassation, France's highest court for judicial matters, ruled that Bessette's actions in the case had been unlawful.

"What he did was completely underhand, and an underhand investigation is fortunately punished in a law-abiding country," Eric Dupond-Moretti, a member of Benzema's legal team, told L'Equipe at the time.

"We'll now see what the consequences are of this ruling. We're leading 3-0 in the 89th minute, but there is still a minute left.

"Of course I would like the whole investigation to be dropped. A policeman who invents a name for himself to call back the supposed blackmailers and start them off again is quite amazing.

"In this case, when they saw the names Valbuena and Benzema, the investigators felt wings grow."