Uefa has warned clubs they will be held responsible for provocative comments made by their coaching staff.
Chelsea boss Jose Mourinho had accused referee Anders Frisk of meeting with Barcelona boss Frank Rijkaard during their Champions League tie.
Frisk said he received death threats afterwards and retired from refereeing.
"It is the club's responsibility if coaches destabilise the opponents as a preparation for matches," said Uefa chief executive Lars-Christer Olsson.
He said: "Especially if that runs the risk of provoking bad behaviour by the fans."
Mourinho received a two-match touchline ban following his comments.
But speaking at a meeting of Uefa's executive committee Olsson added new, stronger punishments will be introduced.
And he said that clubs who fail to control their supporters will also face stronger punishments, which are expected to be introduced in June.