Top sports lawyer Mel Goldberg has warned Manchester United that reporting Real Madrid to FIFA over their pursuit of Cristiano Ronaldo would have little effect.

Goldberg believes United would have a good case if they did decide to take their case to world football's governing body.

But he has forecast that, even if the Spanish giants were found guilty of breaking the rules, any punishment would be minimal.

Goldberg, of Mel Goldberg and Co, said: "If Real Madrid are reported to FIFA, they will probably get a rap on the knuckles.

"I don't know whether they would be expelled from, for example, the European Cup or whether they would be deducted points in the league.

"What FIFA would probably say is you cannot keep a player against his will if he is not happy and wants to go elsewhere.

"They would give some minor castigation and the deal would go through."

United, reportedly prompted by their furious manager Sir Alex Ferguson, last week threatened to call FIFA in as the saga over the 23-year-old Portugal international's future dragged on.

Goldberg continued: "He is under contract and Manchester United can keep him at Manchester United.

"There have already been suggestions they would put him in the reserves and leave him there for a couple of years until his contract runs down.

"But that's not good for United, it's not good for Cristiano Ronaldo and it's not good for the bank balance in as much as in two years' time, he could move for nothing.

"Look at the situation with Thierry Henry. I understand there was a time when an offer came in for him when he was under contract to Arsenal and playing at his best from one of two top Spanish clubs of £50million, which was rejected.

"Then the following year when his form had dropped a little and he wasn't as fit as he used to be, they took £16million.

"They lost a packet on him."

What implications that would have for the regulations on transfers and their enforcement is a matter for debate, but Goldberg admits that the money involved means the game's biggest clubs are unlikely to be punished severely even if they are proved to have done wrong.

He said: "I am sure there have been cases of this nature, but I can't remember FIFA taking on a major club and hammering them.

"I cannot see anybody taking on clubs like Manchester United or Real Madrid, who have got money to fight it, and hammering them."