Full fight report More photos from Las Vegas

Mosley won the fight for the WBC and WBA super welterweight titles on a points decision, leading to widespread booing among the Las Vegas crowd.

But De la Hoya, who was looking to avenge defeat to Mosley for the WBC welterweight title in 2000, was clearly shocked by the decision and said he was prepared to spend part of his $17m purse on an investigation.

"I feel something is wrong," said de la Hoya. "I will get to the bottom of this. I am not doing this because I am a sore loser.

"I feel the decision should have gone to me. On Monday I will push for a full investigation."

De la Hoya, who refused to be drawn on whether he would go through with his pledge to retire if he lost the fight, said the numbers show he clearly won Saturday's rematch.

"I threw 615 punches to his 500 and landed 106 jabs to his 33 jabs," he said.

I was in control physically - I think I was the stronger fighter Shane Mosley

"I have the finances to put the best lawyers on it. Boxing does not need this. I am getting tired of this."

Floyd Mayweather, De la Hoya's trainer, also blasted the decision and said his man fought a perfect fight.

"These old judges are blind and senile. Clearly Oscar won the fight." said Mayweather.

"He got a little tired in the eleventh but he picked it up in the 12th. I don't know what he has to do to win a fight."

All three judges scored the fight 115-113 for Mosley, and all three gave Mosley the last four rounds, meaning De la Hoya's protest is likely to fall on deaf ears unless his lawyers can find evidence of malfeasance.

"These are honest men and they scored the fight the way they did. To me, there is no controversy," said Marc Ratner, director of the Nevada Athletic Commission.

It was the worst decision for a much-touted fight I have ever witnessed From Gene Johnson, California Join the debate

"It's a close fight that could have gone either way. This is the way the judges saw it. If it went the other way, Mosley's camp would have been the ones protesting."

Mosley's trainer and father Jack was heard imploring his son to produce something spectacular as the fight looked set to be decided on points.

"My father was trying to convey to me since we're in Las Vegas and it's Oscar's town, we had to pour it on in the last rounds," insisted Mosley.

"I was in control physically. I think I was the stronger fighter. All I know is I won the fight."