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The Portugal star admits he is unfazed when people question his form on the pitch, and admitted he would love to remain involved in football when he retires from playing

Real Madrid forward Cristiano Ronaldo insists that he is not affected by criticism of his performances on the pitch, stressing that it is simply part of football.

The Spanish champions have endured a mixed campaign to date, with inconsistencies in their domestic form seeing them all-but-yield their title to rivals Barcelona, while they must negotiate a tough second leg against Manchester United to progress to the quarter-final stage of the Champions League.

Although Ronaldo himself has largely maintained his exceptional standards - scoring 37 goals in as many games so far this season - he accepts that being judged on your achievements is part of life at the top echelons of the sport.

"Real Madrid are the biggest club in the world, and people always expect us to be perfect. I think there is always room for improvement," he told GQ magazine.

"Criticism is part of our business; we have to live with it. The thing that hurts me the most is criticism about things away from the field of play. It doesn't bother me when it's about my playing form, because, I repeat, I am the first to realise it when things are going badly."

Ronaldo also dismissed notions that he has formed something of a clique with his Portuguese-speaking team-mates at the Santiago Bernabeu, stating: "I have lots of friends in the dressing room, not just my compatriots."

Real Madrid take on Manchester United on March 5 in the second leg of their Champions League tie, and the 28-year-old has once more revealed his admiration for former boss Sir Alex Ferguson as he prepares to take to the Old Trafford pitch once more.

"I have nothing but gratitude for Ferguson. He is fantastic, as a coach and as a person," Ronaldo said.

Finally, Ronaldo spoke of his hopes for the future of the Portugal national team after their strong performances in recent tournaments, and revealed his desire to stay in football once his playing days come to an end.

"It is much harder to win with the national team than with the club, although we are still a young team," he acknowledged. "We reached the [European Championship] final in 2004, the semi-finals in [World Cup] 2006 and in last year's European Championship; that's an achievement.

"Football is my life. I would love to stay in this world, even after I stop playing. But, for the moment, I'm going to concentrate on the years I have left as a player. Time will tell what will happen next."