Neil Lennon, the Celtic manager, angrily claimed the Spanish referee Alberto Mallenco was "pro-Juventus" after his side crashed to a 3-0 defeat in the first leg of their Champions League last 16 tie.
Celtic were undone by goals from Claudio Marchisio in each half and a late strike from Alessandro Matri which leaves them with a mountain to climb as they head for the second leg in Turin at the start of next month.
However Lennon saved his anger for Mallenco, who repeatedly failed to deal with the shirt-pulling that hindered his side at corners and set-pieces.
"I thought he was poor," claimed Lennon. "I thought he was pro-Juventus.
"They were fouling at every opportunity. The referee was warned by our players to keep an eye on it, and he ignored our requests," Lennon added. "He was staring right at it. So are the rules different in Spain as they are in Britain? Because, on that showing, they must be.
"We played Juventus in 2001 here and I think [Paolo] Montero was marking Chris Sutton. The referee warned Montero and he persisted, so the referee ended up giving a penalty. We won the game 4-3. So what is the difference? That's what I want to know. What is the Spanish interpretation of that?"
Lennon approached the Spanish official at half-time with his side trailing 1-0 but it was to no avail."I pointed it out to the referee at half-time in the tunnel area, but he just waved me away," he said. "I made it clear to the players to flag it up to the referee. They were being fouled, manhandled. It's not rugby we're playing, it's soccer. I'd like to know what the interpretation of the rules are, because it's blatantly different to what I've seen tonight."
The England manager, Roy Hodgson, was at Celtic Park to watch Gary Hooper, who is on the brink of a call up by the national side. Hooper was booked for clashing with Juventus midfielder Stephan Lichtsteiner when they grabbed each other at a first-half corner.