Manchester United have hit back at Sepp Blatter after the Fifa president claimed that Cristiano Ronaldo should be allowed to leave Old Trafford. Blatter's remarks in a television interview in which he criticised a trend towards “modern slavery” in football have surprised the Champions League winners and the game at large.

United are adamant that Ronaldo will not be leaving even though the Portugal winger continues to send out mixed messages about his future. Real Madrid have made no secret of their admiration for Ronaldo, who is recovering from ankle surgery after playing for Portugal in Euro 2008.

"All our players - like at other clubs - enter into their contracts after an open and free negotiation,” a United spokesperson said. "Most of whom do so after taking advice from a Fifa-registered agent. Many do so on a number of occasions and enjoy long and successful stays at Old Trafford."

When Blatter was asked if he felt sympathy for Ronaldo's current position, he said: "Absolutely, absolutely. Definitely as a footballer and the FIFA president, I'm very in sympathy with the player Ronaldo.

"I think in football there is too much modern slavery, transferring players or buying players here and there, and putting them somewhere. And we are trying now to intervene in such cases."

Blatter’s intervention has also been condemned by Uefa, who have stressed that they are more concerned with players wages spiralling out of control.

"It would be useful to remind people that slaves in all of the slavery systems never earned a wage," William Gaillard, Uefa’s communications director, said. "It seems that both clubs and players are trying to negotiate an exit before the player is free. It is a consequence of the Bosman ruling - there is nothing we can do about that.

"It is obvious that today players have a lot more power than they did 20 years ago, undoubtedly, and agents have a lot more power than they did 20 years ago. It is true that salaries are spiralling out of control. Many clubs have pointed that out."

The Bosman ruling came into effect in 1995 and allows players to move on free transfers at the end of their contracts.