Cristiano Ronaldo has said the referee Chris Foy was wrong to book him for diving during the Carling Cup final victory over Tottenham Hotspur.

For the second weekend running, the Manchester United winger was cautioned for going to ground, this time under a challenge from Tottenham's Ledley King.

Officials seem now to be taking a hardline approach with the world player of the year when he goes down in the penalty area. Television replays showed King made contact with the 24-year-old, although even Sir Alex Ferguson admitted he was not certain whether it should have been a penalty or not.

However, the yellow card was harsh, even if Ronaldo refused to be too annoyed with Foy.

"If you see the replay you will see that their player kicked me in the foot," said Ronaldo. "The referee did not make the right decision then and he didn't give me a lot, all match, I don't know why. But in every game, the referee's decision has to be respected."

Ronaldo had no hesitation in taking a penalty in the decisive shoot-out – United's third – even though he missed against Chelsea in last season's Champions League final in Moscow.

"It's always important to choose a side and put the ball there," he said. "After Moscow I thought the goalkeeper would think I put it in the same corner but I changed."

The triumph brought United their second trophy of the season, having been crowned Club World Cup champions in December. An unprecedented quintuple is still on for Ferguson's side.

Yet even a player as confident as Ronaldo accepts the task is fraught with difficulty. "It is quite hard," he said. "We have to think game to game. We won this cup now, we are top of the league and still in the Champions League and FA Cup.

"With United there is always an opportunity to win everything but we need to keep our feet on the ground."