Celtic legend Billy McNeill claims referees in Scotland have favoured Rangers over the Parkhead side for 50 years.
The build-up to Sunday's Old Firm game at Ibrox was dominated by the admission from Celtic, through an unknown source, that they were aggrieved by decisions they believe had gone against them in matches this season - including their first two games against Rangers.
The controversy continued when Hoops skipper Scott Brown was sent off in the 1-0 defeat following a tangle with Light Blues midfielder Kyle Lafferty, who escaped unpunished.
McNeill, who skippered Celtic to their European Cup win in 1967 and who later had two spells as manager, told the Scottish Sun: "Celtic have been suffering referee injustices against Rangers for 50 years.
"The big decisions have always gone against my club and in favour of Rangers. Nothing has changed.
"I felt that way as a player, during two spells as manager and now as a spectator.
"This season I've seen it in each of three derbies - and what happened at Ibrox on Sunday was as disappointing as any I've had to stomach.
"I believe that when it comes to players being red-carded and booked, Rangers have been more favourably treated than Celtic.
"Yes, we have been unfairly treated."