Referee John Beaton has called in police after being targeted with threatening messages online in the wake of last weekend's Old Firm clash, Press Association Sport understands.
The official has found himself at the centre of controversy after allowing Rangers striker Alfredo Morelos to escape punishment during the Ibrox side's victory over bitter rivals Celtic.
Parkhead chiefs have called on the Fifa-listed referee to explain why he did not take action against the Colombian after his involvement in three incidents with three Hoops players.
But Press Association Sport has learned Beaton has now been forced to contact Police Scotland after his work mobile phone number was leaked on social media.
Trolls have since bombarded the official with dozens of threatening and abusive messages and Beaton is now waiting to speak to officers.
Celtic, meanwhile, have also requested a meeting with Scottish Football Association chief executive Ian Maxwell after compliance officer Clare Whyte decided against taking retrospective action against Morelos.
The Light Blues' top scorer appeared to kick out at Hoops skipper Scott Brown, stand on Anthony Ralston and flick out his hand at Ryan Christie's groin area during the victory on December 29 which took Steven Gerrard's team level on points with the Ladbrokes Premiership champions.
However, Whyte was unable to take any further action after Beaton confirmed he saw all three incidents in their entirety during the game.
Celtic released a statement which expressed surprise at the decision and will look to meet with Maxwell and the SFA's head of refereeing, John Fleming.
The statement read: "Celtic Football Club is surprised that there will be no disciplinary action taken by the Scottish FA regarding the incidents during the match on December 29, which have been widely addressed in the media.
"It is reported that no action was taken because the match referee saw all of the incidents in question.
"Given that the referee took no action at the time, this tends to suggest that such conduct, which in one instance led to a Celtic player, Anthony Ralston, being injured, is acceptable in Scottish football. That cannot be right.
"On the day, Celtic did not play well enough to win the match, something we accept. However, this issue goes beyond the result of the match.
"Celtic is not the only club this season to raise concerns regarding the standard of officiating at matches in Scotland, concerns which have also been shared by many commentators on the game.
"In order to fully understand what is going on, Celtic, our supporters, Scottish clubs and the general Scottish football public need transparency in these matters, and we therefore call on the Scottish FA to allow the referee, John Beaton, to explain these decisions publicly as well as any match officials involved in other similar circumstances.
"In the meantime, we have requested a meeting with Scottish FA chief executive, Ian Maxwell, and the Association's Head of Refereeing."
In response, a statement from the SFA read: "We welcome discussions with any of our member clubs.
"The board discussed this last month and it was agreed that we would arrange a meeting involving stakeholders including managers, our referee operations department and PFA Scotland.
"This will be an excellent opportunity to open dialogue, answer questions and discuss opportunities to improve our game."
