The referee at the centre of the Yaya Toure racist abuse storm has been criticised for failing to follow UEFA procedures.
The Professional Footballers' Association say referee Ovidiu Hategan should have reacted decisively once the midfielder complained about the chanting during Manchester City's Champions League game against CSKA Moscow on Wednesday night.
The Romanian official was supposed to have ensured a stadium announcement was made in the Russian capital warning fans the racist abuse had to cease - and then stop the game if it continued.
PFA deputy chief executive Bobby Barnes, who is also European president on the international players' union FIFPro, said: "We're very disappointed that a clear agreed protocol which is designed to deal with these situations was not effected.
"The player, having done what was asked of him to notify the referee, quite rightly expected that the referee would go to speak with the safety officer.
"The (UEFA) protocol is that the safety officer should make a stadium announcement warning the fans that if the chants do not desist then the game will be stopped."
Barnes added: "The player is very upset, as indeed are other players; not just black players but all players at the club.
"I would certainly hope in line with the hard-line stance that UEFA has stated and intends to use in these circumstances they will make a meaningful sanction in this case. It's important we send a message now."
Kick It Out chairman Lord Herman Ouseley also raised the issue of the referee's handling of the complaint by Toure.
Ouseley said: "The referee's job is to protect players. Why did he not do his job, stop the game and deal with it?
"FIFA president Sepp Blatter has made it quite clear that no player should have to deal with that kind of abuse and that if you are a referee you should stop the game."
City lodged a verbal complaint with the UEFA match delegate on Wednesday night and are expected to follow that up in writing today.
UEFA are investigating the allegations and have warned that clubs will no longer escape with just fines if their supporters are guilty of racist abuse.
A first offence of racist behaviour by supporters carries a sanction of a partial stadium closure and a second offence leads to a full stadium closure plus a fine.