Former referee Des Roache has branded a banner aimed at Douglas Ross during Saturday’s Scottish Cup tie between Celtic and St Mirren as “unacceptable”.

The Scottish Conservative leader was targeted with a message from supporter group The Green Brigade during the Parkhead contest, as he ran the line as an assistant referee on the Main Stand side of the pitch.

The banner was unfurled with the message “VAR DECISION: DOUGLAS ROSS IS A C***” as the video technology reviewed Daizen Maeda’s opening goal of the game for Celtic.

On the message from the stands, ex-whistler Roache told Grosvenor Sport: “It all filters down, it’s impressionable. We see young players replicating the way Ronaldo scores, his celebration.

“And now, unfortunately, you see them replicating surrounding the referee regarding a decision.

“If kids see a banner such as what was released at the weekend, is that going to filter down? That it’s acceptable to unfurl that banner?

“It’s not. If my son asks me what that means, what am I supposed to answer?

“And look at the size of the banner. I want to know: How does that get allowed in there in the first place?

“Douglas is a lovely guy, he’s going about his job, doing his thing professionally. For someone to talk about you like that, it’s unacceptable.”

Speaking about the banner yesterday Ross revealed that he took notice of the message during the match.

He said: “Look, I saw the banner being unveiled. I don’t think anyone could have not seen it given the size it was. 

“My duty at Celtic Park was to run the line, be an assistant referee, to support the refereeing team and that was where my focus was for the entire 90 minutes. 

“Others are looking into this. My focus during 90 minutes is to get my decisions right and I am just glad that on the day my decisions were correct. 

“You know we had a good Scottish Cup tie. Six goals, competitive up until a sending off and that changes the nature of the game.  

“Ultimately my focus is on the pitch and others can make comments about my role as a referee and as a politician. But for 90 minutes my focus is on the football.” 

The match was shown live on Viaplay and commentator Rory Hamilton was forced to apologise if any viewers were offended by the message. 

Co-commentator Michael Stewart responded, adding: "VAR is very controversial, Rory!".