Police are investigating claims that referee John Beaton was targeted with threatening messages and phone-calls in the wake of last weekend's Old Firm clash.

Beaton was criticised for failing to punish Alfredo Morelos who appeared to kick-out at Celtic captain Scott Brown during the match which finished 1-0 to Rangers.

And in a statement released on Friday Celtic called on the Fifa-listed referee to explain why he did not take action against the Colombian after his involvement in three incidents.

But Beaton has now been forced to contact Police Scotland after being harassed with dozens of threatening messages and calls after his mobile phone number was leaked on social media.

A Police Scotland spokeswoman has now confirmed that they are investigating the incident.

A statement given to STV News said: "We can confirm that a complaint has been made to police regarding texts and calls received by a 36 year-old man.

"Police enquiries are ongoing into this matter."

In a statement released on Saturday Ian Maxwell, Chief Executive of the Scottish FA, said:

"It is with deep dismay, that in the last 24 hours, we learned of one of our match officials having had threats made against him and his family.

"We are in close contact with those involved and with Police Scotland to ensure that they are safe and that those responsible are identified and held accountable for their actions.

"This is not the first time in recent weeks that our match officials have been targeted. Another referee was allegedly threatened and assaulted at a lower-league game prior to Christmas. These incidents are isolated but are they are unacceptable and extremely concerning when they occur.

"Our match officials make hundreds of decisions each game. They take huge pride in their work but it is inevitable and accepted that some of their decisions will be viewed differently and debated by others. When differences of opinion however manifest as threats to our officials or their families, a line has been crossed.

"Match officials are a vital part of the game and they work exceptionally hard to maintain high standards. We all have a responsibility to support our match officials and, as previously stated, we will shortly be engaging with stakeholders to allow them to discuss issues, air concerns and propose improvements to this area of our game.

"As we look forward to 2019, I call on everyone involved in Scottish football, from the public parks to the international stage, to respect our match officials."