After referee Mark Halsey's claims of texts with former Manchester United manager Alex Ferguson, Premier League referees have been warned not to speak to managers by the Professional Game and Match Officials Ltd.
According to the Mirror, the Hertfordshire official retired at the end of last season, the same time as Sir Alex stood down at Manchester United.
It is Halsey's texting claim, however, that has sparked fresh controversy, the report said.
The ex-official claims that he asked the Scot to defend Clattenburg over allegations that Mikel had been called 'a monkey' in the October 28 fixture, the report added.
Halsey said that he took matters in his own hands and rang Sir Alex asking him to speak out, adding that it took time to gain the manager's respect but in the end they had a very good relationship.
Halsey's comments have stunned football fans fearful that relationships between referees and managers could influence results, the report further said.
The Professional Game and Match Officials Ltd, the body that appoints officials for top-flight matches, were made aware of Halsey's book and briefed all of their referees ahead of the allegations and referees contravening the guideline would be subject to disciplinary action if any case against them were proved, according to the report.