Manchester City boss Manuel Pellegrini is facing the likelihood of disciplinary action from UEFA after accusing Swedish referee Jonas Eriksson of lacking "impartiality" during the 2-0 defeat by Barcelona.
Pellegrini said Eriksson was "on Barcelona's side from beginning to end" and was trying to make up for a previous mistake against the Catalan side, and also questioned UEFA's decision to appoint an official from Sweden for the Champions League last 16 first leg match.
UEFA is likely to take a dim view of such comments - in 2011 it banned Jose Mourinho for five matches, reduced on appeal to three, for a similar rant when he was at Real Madrid.
Pellegrini's comments overshadowed a game which was decided by Lionel Messi's penalty, which led to Martin Demichelis' dismissal, and Dani Alves' last-minute strike.
The City manager claimed the foul by Demichelis was outside the box and that Eriksson - who has been selected by FIFA as one of the referees for this summer's World Cup in Brazil - should have given City a free-kick earlier in the move for a challenge on Jesus Navas by Sergio Busquets.
"I felt the referee was not impartial so he decided the game with a foul that he didn't whistle against and a penalty with Demichelis that was not a penalty, it was outside the box.
"He did not have any control of the game. He was on the side of Barcelona from the beginning until the end.
"I think it was not a good idea to put a referee from Sweden in charge of such an important match, especially a referee who has made an important mistake against Barcelona in a previous match."
Dan Hewitt takes a look at an historic night for Manchester City
Thousands of Barcelona fans are in Manchester ahead of the Champions League clash with Manchester City at the Etihad stadium.
Barcelona fans catching the tram to tonight’s Champion’s League game will get a warm Spanish welcome from Metrolink and Manchester City.
City star Pablo Zabaleta has recorded welcome greetings in Catalan, Spanish, and English to be played at the Etihad Campus tram stop.
Argentinian international Zabaleta’s message will thank City supporters for their amazing support and for using the tram to get to the match, as well as wishing Barca fans a nice stay in Manchester.
Manchester City are gearing up to face Barcelona in the knockout stages of the Champions League.
They will host the Spanish giants in the first leg of their last 16 tie at the Etihad Stadium tonight.
It is the first time the two sides have met in a competitive match.