The International Rugby Board (IRB) has warned coaches and players against criticising referees in public.
IRB chairman Bernard Lapasset has written to unions across the game ahead of the RBS 6 Nations, reminding them of their responsibility to maintain "discipline, integrity and respect" when commenting on match official performance.
The tournament kicks off on Saturday, with Wales hosting Italy and England travelling to France.
"Rugby values its culture of respect for the opposition and match officials, which is at the very heart of the Game," said Lapasset in a statement released by the IRB.
"But there has been a slow increase in the level and intensity of public criticism of match officials and their performances from coaches and players.
"Match officials, like players, do make mistakes, but it is important that we work with our unions to ensure that match official performance is discussed within the appropriate and established framework for feedback and appraisal that operates between coaches, match officials and the IRB."