English football is in danger of being dragged through another racism saga after police launched a formal investigation into whether Mark Clattenburg used inappropriate language" towards Chelsea stars John Obi Mikel and Juan Mata.
The Metropolitan Police confirmed they had acted on a "complaint" from the Society of Black Lawyers after the Blues accused referee Clattenburg of using comments understood to have been interpreted as racist in the club's acrimonious defeat to Manchester United on Sunday.
Press Association Sport understands the 37-year-old completely rejects the allegations against him, which are also the subject of a Football Association investigation.
A police statement read: "An investigation has been launched into alleged comments made during a football match between Chelsea FC and Manchester United FC at Stamford Bridge on 28 October 2012.
"Officers from Hammersmith & Fulham borough are in liaison with Chelsea Football Club and the Football Association. We continue to work in partnership with Chelsea Football Club and the Football Association in order to consider any allegation that is made in relation to the reported events."
The criminal probe came less than 24 hours after the FA launched their own investigation. However, they could yet postpone it if the police request they do so, something they came under heavy fire for during the John Terry scandal.
The Metropolitan Police became embroiled in their second high-profile football racism case in 12 months after the man behind the mooted black players' breakaway union, Peter Herbert, wrote to them demanding an investigation. He defended his intervention on Tuesday afternoon, telling Sky Sports News: "What we don't want is for it to be swept away under the carpet. It must be subject to a full and proper investigation."
It is understood Clattenburg had yet to be interviewed by the FA on Tuesday morning but was ready to deny any wrongdoing, having vowed to co-operate fully with any investigation. He is said to have been shocked and angered at the allegations made against him and confident of clearing his name. He is now expected to be spoken to by both police and the FA, possibly after submitting a written account about what took place during Sunday's Barclays Premier League game at Stamford Bridge.
Clattenburg has already filed what is known as an 'extraordinary incident report', which is understood mainly to deal with an alleged confrontation that took place in the referees' room after full-time. Sources have told Press Association Sport Chelsea manager Roberto Di Matteo, assistant manager Eddie Newton and chief executive Ron Gourlay were all present as Mikel angrily accused Clattenburg of having abused him during the match itself.
The referee, his assistants and fourth official are understood to have been stunned by the claims, with Michael McDonough, Simon Long and Michael Jones - who were miked up to Clattenburg - denying hearing anything of that nature. The situation appears to have been complicated by suggestions that neither did Mikel or Mata, with reports claiming they were informed of the alleged abuse by team-mates. Midfielder Oriol Romeu was quoted as having told a Spanish radio station that Mata had confirmed as much.