Chelsea has made a formal complaint against referee Mark Clattenburg after accusing him of using "inappropriate language" to two of its players in the controversial defeat to Manchester United.
The European champion confirmed it had reported Clattenburg to the Premier League match delegate after the fiery 3-2 loss at Stamford Bridge.
A club spokesman said: "We have lodged a complaint to the Premier League match delegate with regards to inappropriate language used by the referee and directed at two of our players in two separate incidents in today's match.
"The match delegate will pass the complaint to the
"We will make no further comment at this time."
Clattenburg tonight insisted he would co-operate with any investigation.
Professional Game Match Officials (PGMO), the body which represents Premier League referees, released a statement which read: "PGMO is aware of the allegations and they are being treated with the utmost seriousness.
"Mark will co-operate fully and welcomes the opportunity for the facts to be established.
"No further comment will be made until this matter has been properly investigated."
All four officials - the referee, his two assistants and the fourth official - wear microphones and ear pieces that allow them to hear what each other is saying throughout the match. What is said between them is not recorded.
The revelation that Chelsea had made the complaint rounded off a dramatic day which saw the London side lose its unbeaten top-flight record after
English Premier League
Rafael Benitez quietly slipped out of Chelsea as the UEFA Europa League winner ended its season with a 5-3 friendly loss to Manchester City at Yankee Stadium.