UEFA Cup semi-final: Celtic striker John Hartson criticised Belgian referee Frank de Bleeckere after last night's UEFA Cup draw with Boavista.
He believed that match official clearly saw two handball incidents in the Boavista area in the first period but refused to award a penalty to Celtic.
Welsh international Hartson was even less impressed with the referee's time-keeping at the end of the game when his assistant flashed up three minutes of injury time.
Hartson said: "Those (the handball incidents) are some of the things you have to put up with in Europe - and I don't know where he got three minutes from.
"I would like to watch that game again because I think there must have been at least 10 minutes. I know 10 minutes can't go up on the board but I don't know where he has got three minutes from."
Hartson warned Boavista that Celtic had already proved themselves in second legs following home draws. He said: "We played quite well in patches but their goal killed us a little bit at the start of the second half.
"They are a decent side and have good players but we drew at home to Blackburn and Liverpool so there is still all to play for. With the players we have in our side, we can get an away goal so we are still in this tie."
Celtic manager Martin O'Neill said: "The players are disappointed in the dressing-room for a number of reasons - but there's nothing to be disappointed with.
"We're in the UEFA Cup semi-finals, it's the first time Celtic have been involved in European football after Christmas for 23 years and the players have given everything.
"There's a bit of frustration - but we're not finished yet. There's a big prize at stake in Portugal in two weeks - we'll go for it with everything.
"Next week will be our 14th fixture in Europe and I think the players are entitled at this stage to be a wee bit tired.
"But we'll draw confidence from Liverpool - we were able to win there and we think we can do it again in Portugal." O'Neill also admitted he was frustrated by some of the "play-acting" by the Boavista players.
"You have to try and play the game fairly but unfortunately rolling around, staying down and feigning injuries is a major part of the game and it's very disappointing.
He added: "They came here to do a job and that's what they did. They tried to kill the game at every opportunity."