Madrid: Two-time World Player of the Year Cristiano Ronaldo slammed referee Alberto Undiano Mallenco after Real Madrid were beaten for the first time in 32 games 4-3 by Barcelona on Sunday.
Mallenco awarded three penalties on the night with Ronaldo scoring the first one for Madrid to put them 3-2 up 10 minutes after half-time.
However, Sergio Ramos was then sent-off for denying a clear goalscoring opportunity for a foul on Neymar inside the area before Xabi Alonso was adjudged to have tripped Andres Iniesta seven minutes from time.
Lionel Messi converted both spot-kicks to complete a hat-trick after cancelling out Karim Benzema's double at the end of the first-half to become the all-time leading scorer in games between the two sides.
"There were a lot of mistakes for just one game. A match between Real and Barca ought to have a high level of referee," said Ronaldo.
"You can't make correct decisions when you are nervous. It makes me think that it is not just on the field that you win games, a little help from outside helps too.
"My penalty might have been just outside the area, but there are many things that went on. It is difficult when many people didn't want us to win today."
Ronaldo's coach Carlo Ancelotti was more level-headed about Mallenco's decisions, but did agree that Ramos' red card swung the game in Barca's favour.
"I haven't seen it again and it is difficult for me to comment on the decisions of the referee because there were many.
"However, it was the key moment. We were winning 3-2 and controlling the game well, but it is much more difficult to control the game with a player less."
Defeat leaves Madrid still joint top of the table on 70 points alongside Atletico Madrid, but in second place due to their inferior head-to-head against their local rivals with Barca a point further back in third.
And Ancelotti is seeking a immediate response from his side with a difficult looking away game against in-form Sevilla to come on Wednesday.
"Obviously we are not happy because we have lost a big opportunity, but we will continue fighting until the end.
"There are nine games left and it will be an intense race. The league is open for all three teams and any game could be decisive.
"We need a good reaction on Wednesday because that could be the key game of the season."