Celtic manager Neil Lennon has described the performance of referee Bobby Madden as "appalling" after his side was held to a 1-1 draw against St Mirren on Sunday afternoon.
Madden sent off Bhoys midfielder Victor Wanyama 10 minutes into the second half and also awarded the home side a controversial late penalty from which Paul McGowan equalised.
After the game, Lennon was scathing in his assessment of the official's performance as Celtic continue to stumble towards the Scottish Premier League title.
"That is by far the most appalling refereeing performance I've seen this season," the Celtic boss told the BBC. "How he got so many big decisions wrong in one day is beyond me."
Kenya midfielder Wanyama was shown a straight red card for a tackle in the centre circle in the 55th minute, and Lennon was adamant that the club would contest the decision.
"Absolutely," he replied when asked if the club would appeal the sending off. "It's absolutely awful.
"Beram Kayal was thrown into the advertising boards and five seconds later my man gets sent off - which is never a red card. The sending off killed the game as a spectacle.
"And that is not a penalty for St Mirren. It was outside the box and there was no contact.
"I've been pretty concerned for the last couple of months about the abhorrent decisions I've seen - not just against my team but in general in the Scottish game."
Lennon admitted his side were lucky to get away without conceding a spot kick earlier in the half after Greece striker Georgios Samaras appeared to handle the ball inside the area.
"It's a clear penalty," the Northern Irishman added. "Samaras has handled the ball. How he doesn't see that and the linesman doesn't see it is beyond me.
"We're talking about the referee rather than the competitive nature of two good footballing teams. I haven't said anything insulting or called the referee's competence. I just thought he had an appalling game."
Celtic have now failed to win any of their last four away games in the SPL, and Lennon admits to having some concerns over his side's form as they enter the final straight of the campaign.
"We looked okay at the start of the second half, without being brilliant, but never really settled," he admitted. "Our ball retention should have been better, even with the 10 men.
"I'm a bit concerned. There's still a few of them not finding their best form. I don't know why. We've got a week now to get ready for Hibs and I want to start seeing performances at the level I expect."