The comments are set to land City's manager in serious trouble with UEFA, especially after he suggested that Eriksson was trying to make up for making an error against Barcelona in a previous match against AC Milan.
said: "From the beginning I felt the referee was not impartial to both teams 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."
Pellegrini appeared to be referring to the 2012 Champions League quarter-final when Eriksson was criticised by then-Barcelona coach Pep Guardiola for failing to award his side two penalties in the first-leg's goalless draw at the San Siro.
Pellegrini claimed Eriksson should have given City a free-kick in the build-up to the move that led to the penalty award for a foul on Jesus Navas.
He added: "I think that the referee decided the game because before the penalty there was a foul on Navas three metres away from him so he could see it without any problem.
"The more important mistake is the foul against Navas and secondly the penalty.
"Contact was outside the box - that is the foul, you cannot continue the foul. The first foul is outside the box.
"Before the penalty Barcelona did not have chances and we were preparing the way to score.
"Playing 40 minutes with one player less is very difficult against Barcelona. We played well and tried to draw and in the last minute they scored the second goal."
The Chilean was asked to explain his comments that UEFA should not have chosen a referee from Sweden.
He replied: "More important football in Europe than Sweden. A big game with two important teams, that kind of game needs a referee with more experience."