A furious Manuel Pellegrini accused the referee, Jonas Eriksson, of deciding Barcelona's 2-0 win over Manchester City in the Champions League by rectifying mistakes made when officiating a previous tie involving the Catalan club.

The match Pellegrini referred to was a quarter-final two years ago at San Siro between Barcelona and Milan that ended goalless, with the former coach, Pep Guardiola, complaining about two penalties Eriksson failed to award his side.

After Barça won Tuesday's last-16 opening leg at the Etihad, Pellegrini claimed that Martín Demichelis's second-half challenge on Lionel Messi was not a penalty and the central defender should not have been sent off.

After Messi scored from the spot after 54 minutes a valiant 10-man City held out until Daniel Alves secured a late second for Barcelona that makes them firm favourites to progress to the quarter-finals when the return leg is played on 12 March.

Eriksson awarded the penalty when Demichelis tried to tackle Messi in a challenge that may have started marginally outside the area. Asked what his view of the incident was, Pellegrini said: "The referee decided the game.

"Before the penalty it was a foul on [Jesús] Navas when he [Eriksson] was three metres from the play so he could see it. From the beginning I felt the referee was not impartial to both teams. So he decided the game. And after it was not a penalty, it was outside the box.

"The contact was outside the box, that was the contact. You cannot continue the foul, the first foul was outside the box. But the important mistake is the foul against Navas, the second mistake was the penalty. But it was from the beginning [Eriksson's impartiality].

"Barcelona did not have chances before the goal. It was a pity because that important action decided the game. Playing 40 minutes with one player less is difficult against Barcelona but we played well with one player less and in the last minute they scored the second goal."

Pellegrini walked on to the pitch at the end of the match to confront the Swedish official. "It was just to tell him he decided the game. I was not happy because he decided the game," said the manager, who could face Uefa censure for his remarks. "He did not have any control of the game. He favoured Barcelona from the beginning to the end. I think it was not a good idea to put a referee from Sweden in charge and a referee who made a mistake against Barcelona in the group stages."

Asked if Eriksson was compensating for his perceived mistakes at San Siro, Pellegrini said: "Yes."

Pressed what difference Eriksson's nationality made, Pellegrini said: "I think there is more important football in Europe than Sweden. A big game with two important teams – that kind of game needs a referee with more experience. This referee whistled the Barcelona-Milan game and he made an important error against Barcelona. Today he remedied it.

"Yes, Barça had a lot of the ball but they had it where we wanted. They were not near our area so they did not create in our area. The referee from the beginning did not give a good impression. There was a penalty, we had one player less but the team played with courage."

Eriksson, who is on the Fifa list for this summer's World Cup, has been at the centre of other controversies, with the most recent coming during the group stages when he might have sent off Borussia Dortmund's Robert Lewandowski in Arsenal's 2-1 defeat at the Emirates.

Despite the daunting task that now faces them at Camp Nou, Vincent Kompany believes City can still progress. "By no means we thought they were superior. When it was 11 v 11 maybe we showed a bit too much respect in the beginning," the City captain said. "They were there for the taking."

He claimed Barça are not the best side City have faced. "Not at all – they are incredibly efficient, though – they have great individual quality," said Kompany, who also referred to Eriksson's display. "There was a lot of soft fouls. In the Premier League they would have not been given.

"If the tempo was greater in this game it would have been to our advantage. If the game is the same as today, and we manage to stay away from some fouls, we have got a chance [in the second leg]."

Cesc Fábregas, who impressed for Barcelona throughout, said: "We had a great result. The fans put so much pressure on and that's what makes this win so special.

"We had a point to prove and we did it very well. Some people were talking a bit too much before the game and now they have to shut up for a few days. We are top of the league, we had a good result here and we are in the final of the [Copa del Rey]. There's nothing else you can ask for. You never know in football but in three weeks we will have to play very well."

The Barcelona head coach, Gerardo Martino, refused to get carried away by the result, pointing out that City had beaten Bayern Munich away from home in the group stage. "I am not confident but we have had a good game away from home and we just have to repeat the same performance. We must not forget that City lost to Bayern Munich at home and then they won away."