Pacquiao issued a statement on Wednesday through his office as a senator, endorsing a letter from the country's Games and Amusements Board for a thorough review of the judges and referee who oversaw the bout.
"On my part, 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".
Pacquiao also stressed that he will dip his fingers into the selection of judges and referee next time, citing the crucial roles they play in a fight.
Through chairman Abraham Mitra, the GAB sent a letter to WBO president Francisco Varcarcel calling for a review of the biggest fight in Australian boxing history.
Pacquiao has admitted he needs to think long and hard about his future after losing to Horn in a gruelling fight.
Meanwhile, Pacquiao backed the decision of the Games and Amusements Board to urge the World Boxing Organization to look into the officiating of his fight.
"The contract for Pacquiao vs Horn provides a rematch clause, which the WBO is in accordance if the promoters decide to move forward", said Valcarcel in a personal message to WBN before later tweeting it on his own account. Despite many being of the opinion that Pacquiao landed the cleaner punches and had a better grasp on the fight, Horn won 115-113 on two of the judges' scorecards and 117-111 on the other.
The WBO on Tuesday responded to the controversy on its Twitter account: "The discretion of a referee or judge can not be reversed, except in a case of fraud or violation of laws which is not the case in Pac vs Horn". Pacquaio also said that he would be ready for a rematch with Horn.
Likewise, Pacquiao lashed at referee Mark Nelson's carefree attitude against Horn's rough tactics.