A 1-1 draw saw the Catalans advance and Barcelona never looked like letting their 2-0 first-leg lead slip in today's encounter at the Nou Camp but the game could have proved more difficult if a Gonzalo Higuain strike early in the second half had not been controversially ruled out.

Pedro then converted a fantastic ball from Andres Iniesta before Marcelo levelled on the night for Madrid.

The disallowed goal was one of the major talking points surrounding the officials and Madrid's Spanish World Cup winner Alonso told Sky Sports 2 that the whole team were upset with what they perceived to be poor decisions.

"When we scored the first goal it would have been totally different and we feel so many bad decisions have been made against us and we are not happy about that," he said.

"We think we did a good job but decisions went against us, we really feel that way."

The former Liverpool midfielder claimed that Higuain's disallowed goal would have altered the nature of the tie in Madrid's favour as the game was still deadlocked at 0-0 at the time.

"It would have changed everything, our position would have been much stronger and after that it was much more difficult," he said.

Madrid manager Jose Mourinho was not at the ground tonight after being sent to the stands in the first leg, but negative comments surrounding his tactics from that game were dispelled by Alonso, who also claimed his Portuguese manager had been able to get his message across before the match

"Until the sending off [of Pepe in the first leg] we were doing really well and it looked like it was going to finish 0-0 and with tonight's result we would have gone through," he said.

"(Mourinho) was really upset that he couldn't be supporting the team in the stadium but he gave us lots of advice before the game."

Barcelona boss Pep Guardiola did not agree with Alonso's opinions on the refereeing of both legs, insisting it was not the main talking point.

"I don't have time for that, it has been a tough 20 days and we have played the richest team in the world many times, the referee may have had an influence but we were very good in the second match," he said.

Guardiola also said he was happy to be returning to the venue where the club won their first European Cup 19 years ago.

"Football is coming home so it an honour to play at Wembley," he said.

"We won our first Champions League in 1992 at the old Wembley and we are ever so proud for our club and players."

The 40-year-old Barca manager thinks Manchester United will progress against Schalke to set up a repeat of the 2009 final which his side won 2-0, but he believes that would have no bearing on any potential rematch.

"I suppose it will be Manchester [in the final], it was two years ago and I think Sir Alex Ferguson will always be there so for us it is an honour and for me as a young coach it is an honour to arrive at the final and play them," he said.