The sport's governing body said last week that the possibility of replacing a red-carded player with a team-mate after 20 minutes was moving closer to global adoption following "successful trials."
The sent-off player would not, though, be able to return for the rest of the match.
The proposed new law is part of a package of changes "designed to enhance the viewing and playing experience," World Rugby said.
In a joint statement, the French rugby federation (FFR), the league (LNR) and the players' union Provale disagreed. Ahead of a World Rugby council meeting next month, they said they were firmly opposed to the adoption of the rule and called on the sport's governing body "to base itself on evidence before modifying such a crucial sanction, particularly with regard to the impact on player safety."
"For the FFR, LNR and Provale, the red card is a crucial tool that deters unsporting behaviour and protects the physical integrity of players," they said. "Transforming this sanction into a temporary expulsion could encourage dangerous behaviour, thereby compromising player safety, which must remain the absolute priority."
Noting that only three red cards were issued at the U20 World Championship, they said that the testing of the rule change in four competitions "where insufficient data has been collected cannot be considered as a convincing reason for improvement before considering a worldwide implementation."
The innovation was introduced by New Zealand in 2020 in Super Rugby to try and manage foul play without impacting the integrity of a match. It has also been trialled in the Rugby Championship.Â
The FFR, LNR and Provale challenged the idea that the new rule will encourage a more fluid game.
"The statistics provided by the FFR to World Rugby show that a red card is not systematically synonymous with defeat for the team penalised," they said. "In fact, an analysis based on 480 Top 14 matches and international matches in Tier 1 shows that only 60 per cent of teams shown a red card lost the match."
The FFR, LNR and Provale also raised concerns that the introduction of the 20-minute red card may damage the image of rugby as it could encourage more aggressive play.
