Chelsea have lodged a formal complaint with the Football Association over language used by referee Mark Clattenburg towards Jon Obi Mikel in the club's controversial 3-2 defeat to Manchester United on Sunday.
The London club insisted they had not taken the decision lightly but decided to press on with their complaint after speaking to all the players and staff involved.
Chelsea have decided there is not enough evidence to submit a second complaint, thought to be for an exchange between Clattenburg and Juan Mata.
"Chelsea Football Club today lodged a formal complaint with The Football Association regarding inappropriate language directed at John Mikel Obi by referee Mark Clattenburg," the statement read.
"This is a result of a thorough investigation carried out by the club, and led by outside legal counsel, of all information available to us including interviews with a number of players and staff.
"Following Sunday's Premier League game against Manchester United, club board members were quickly made aware, upon entering the home dressing room after the final whistle, that there were allegations of inappropriate language directed at Chelsea players by Mr Clattenburg during the game.
"Board members began establishing the details of the allegations, speaking to all relevant players and staff. After those initial interviews it was clear that the matter had to be reported.
"The correct protocol for doing so was to report the incidents to the match delegate, and the club took immediate steps to inform him as soon as he was available. It was not a decision the club took lightly.
"Since reporting the matter to the delegate, the club and outside legal counsel have conducted further investigations. Having completed that process we have now followed the correct protocol and lodged a formal complaint with The FA regarding John Mikel Obi.
"There was not sufficient evidence to support a second claim to the FA with regard to the alleged verbal abuse of another first team player.
"We will cooperate fully with The FA and the Police as they each investigate the matter. As events on Sunday are now subject to those investigations we are unable to comment further until those processes are complete."
Though Chelsea make no mention of what Clattenburg is supposed to have said it is understood the basis of their complaint is the official used language of a racist nature.
Clattenburg has been withdrawn from this weekend's Premier League fixtures by the Professional Game Match Officials, who said if he was deployed he would be under too intense a scrutiny.
The 37-year-old endured a torrid afternoon at Stamford Bridge after he sent off two Chelsea players, including Fernando Torres for diving when he seemed to have been caught by United defender Jonny Evans.
United went on to win the game via a goal from Javier Hernandez, who appeared to be in an offside position, and it is after the winning goal that Clattenburg and Mikel are thought to have clashed.
ESPN revealed on Wednesday Chelsea had sought legal advice on the issue before deciding whether to proceed with their complaint, which is confirmed in the club's statement.
And by emphasising that it is a decision the club "has not taken lightly" Chelsea appear adamant they have a case against Clattenburg, with the divisive fall out from John Terry's FA charge still fresh in their minds.