( CNN ) -- English football has been plagued by racism scandals in the past year , and now its ruling body must deal with what is thought to be the first case of racial abuse by a Premier League referee . League leaders Chelsea made a complaint over `` inappropriate language '' used by ref Mark Clattenburg during Sunday 's controversial 3-2 home defeat by Manchester United . Chelsea 's complaint focused on comments made to two of its players in two separate incidents . Clattenburg had already infuriated the European champions by sending off two of their players , dismissing Fernando Torres for diving even though he had been fouled and then allowing United 's winning goal to stand even though television replays showed it appeared to be offside . With the issue of racism in English football under intense scrutiny , and following in the wake of Chelsea 's own problems with captain John Terry 's ban for racially abusing an opponent , the allegations against Clattenburg come at a time when the Football Association is under pressure to be seen to be taking a strong stance . `` I ca n't think of any previous such incident in the professional game off the top of my head , '' an FA spokesman told CNN . `` In grassroots football , yes , I can recall incidents but in the professional game I would have to check the record books . '' The FA said on Monday they had launched an investigation into the allegations , while Clattenburg has welcomed `` the opportunity for the facts to be established . '' `` We have lodged a complaint to the Premier League match delegate with regard to inappropriate language used by the referee and directed at two of our players in two separate incidents during ( the ) match , '' Chelsea said in a statement said on Sunday . `` The match delegate will pass the complaint to the Football Association . We will make no further comment at this time . '' British media have reported that one of the players involved was Chelsea 's Nigeria international John Obi Mikel . For the past year , the Blues have been at the heart of a racism row after an incident involving Terry and Queens Park Rangers defender Anton Ferdinand during a Premier League match in October 2011 . The FA found Terry guilty of racially abusing Ferdinand , even though a court had earlier cleared the former England captain . The FA -- which requires a lower burden of proof than an English criminal court -- barred the 31-year-old for four games for the incident and also fined him £220,000 . Terry missed Sunday 's Stamford Bridge clash with second-placed United , who now trail Chelsea by just a point , as he served the second game of his ban . Chelsea 's complaint means the FA will now have questions to answer after an allegation against one of its top referees . The body which represents Premier League referees -- the Professional Game Match Officials ( PGMO ) -- said it 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 , '' it said in a statement . All four match officials -- the referee , his two assistants and the fourth official -- wore microphones and ear pieces that allowed them to hear what each other was saying throughout the match . But under the guidelines of football 's world governing body FIFA , what is said between them is not recorded . The allegations against Clattenburg come at a time when the FA is already under fire from several black players , who feel that the punishment meted out to Terry for his racist abuse was too lenient . London 's Metropolitan Police have also launched an investigation after a steward was injured in the aftermath of Manchester United 's winning goal . Scorer Javier Hernandez appeared to be pelted by objects from the crowd while footage emerged of a steward falling over advertising hoardings and onto the pitch . Earlier this month , a number of black players refused to wear T-shirts promoting an anti-racism campaign in protest at a perceived lack of action about the problem from the game 's leading bodies . The Clattenburg case came on the same afternoon as referee Andre Marriner earned the wrath of Everton manager David Moyes , who felt that Uruguay striker Luis Suarez should have been sent off for a bad tackle in Sunday 's Merseyside derby against Liverpool , which ended 2-2 at Goodison Park . Suarez himself was at the center of a racism row earlier this year , receiving an eight-match ban after being found guilty by the FA of racially abusing Manchester United defender Patrice Evra . Four years ago , Evra , who played against Chelsea on Sunday , was banned for four matches and fined £15,000 after clashing with a groundsman at Stamford Bridge , with the FA saying that charges that Sam Bethell used racially abusive language towards the France international could not be proven .
Chelsea filed complaint with English FA over Chelsea 's ` ` inappropriate language '' . Clattenburg reportedly used racial language towards John and Chelsea . FA launch investigation after reading match report from Chelsea on Monday . Clattenburg used opportunity to establish facts in case with few precedents .