Manila - Philippine boxing legend Manny Pacquiao on Wednesday urged the World Boxing Organisation (WBO) to review the "unfair decision and officiating" after losing his welterweight title to Australia's Jeff Horn. 

Pacquiao endorsed a formal call by the Philippines' Games and Amusement Board for the WBO to review the outcome of Sunday's fight in Brisbane. 

"I love boxing and I don't wanna see it dying because of unfair decision and officiating," Pacquiao, 38, said in a statement issued by his office. 

"I had already accepted the decision but as a leader and, at the same time, fighter I have the moral obligation to uphold sportsmanship, truth and fairness in the eyes of the public," said Pacquiao, also a sitting senator. 

In the twilight of a 22-year pro career in which he won world titles in an unprecedented eight weight divisions, Pacquiao had initially called for a rematch, but later said he would also "think hard" about retiring. 

Widely written off by observers, Horn, 29, shocked Pacquiao with his ultra-aggressiveness to earn a unanimous 12-round decision. 

A day after the bout, the Philippines' sports regulatory body wrote the WBO calling for a "thorough review" on the decisions of American referee Mark Nelson and the judges.

"We are making this request for a review, which may call for sanctions on the referee and judges if so warranted, in furtherance of our mutual goal of protecting the integrity of the sport," the board wrote. 

Pacquiao attached a copy of the letter to his own statement. 

"WBO should take appropriate action on the letter sent by the Games and Amusement Board so as not to erode the people's interest in boxing," Pacquiao said. 

The WBO on Tuesday responded to the controversy in its Twitter account. 

"The discretion of a referee or judge cannot be reversed, except in a case of fraud or violation of laws which is not the case in Pac vs Horn," the WBO said.

"The contract for Pac vs Horn provides a rematch clause, which the WBO is in accordance (with) if the promoters decide to move forward." 

While saying he respected the fight outcome, Pacquiao had questioned the referee's decisions and made disparaging comments about Horn. 

"He's not really good but he's really strong," Pacquiao said of Horn on Monday, while the Filipino's camp criticised the referee for supposedly allowing the undefeated Australian to get away with a host of illegal tactics. 

"The problem here is that the referee, I don't know if he did it deliberately or he just did not have experience, he just allowed it and did not even give any warning for how many times," Pacquiao said. 

"It's as if the referee wanted to help my opponent."