Aiden McGeady has accused referee Dougie McDonald of lacking impartiality in Celtic's Old Firm derby defeat at Ibrox.
In an outburst which is almost certain to land the Republic of Ireland winger in trouble with the Scottish FA, McGeady claimed McDonald's performance had been influenced by his club's criticism of officials in the build-up to the game on 28 February.
Just four days before the match with Rangers, an anonymous Celtic source revealed the Parkhead club had met with the SFA to express concerns about refereeing standards.
The claims have sparked a running spat between the Hoops and the SFA, which intensified when McDonald sent off Scott Brown in the 1-0 defeat at Ibrox.
This week has witnessed a series of controversial statements from Celtic in response to the red card and McDonald's refusal to rescind it - but McGeady's claims are arguably the most inflammatory.
He said of McDonald: "The comments before the game might have played on his mind.
"It's safe to say he wasn't impartial the other day. Of course, it didn't look like a red card for Scott Brown."
Celtic were also upset McDonald failed to send off Rangers defender Madjid Bougherra for persistent infringements.
Asked if Bougherra should have been shown a second yellow card, McGeady said: "Yeah, of course."
Pressed further on the official's overall performance, the winger said: "If I told you, I would get into trouble."
Celtic went into Sunday's match at Falkirk 13 points behind Rangers in the Clydesdale Bank Premier League, with manager Tony Mowbray under increasing pressure in his first season in charge.
Speaking in the papers McGeady said: "I'd like to see the manager given time.
"Eight or nine months isn't long enough to stamp his authority on the club.
"Celtic will always be judged on titles and if we don't win it this season a lot of people won't be happy with him and the team.
"There may be calls for him to be sacked or resign but I would like to see him stay. He is a good manager and has a lot to offer."
Mowbray, meanwhile, insists he will never attempt to play more like Walter Smith's Rangers in his bid to bring success to Parkhead.
The Celtic boss, whose refusal to bend from his attacking principles arguably saw West Brom relegated from the Barclays Premier League last season, said: "The bottom line is two coaches that have a different philosophy of football.
"I spoke to Walter about that and he sets his team up as he sets his team up. They've found decent consistency. I just don't play like that; my teams don't play like that."
© Press Association