"It's common sense. Do you see animals mating with the same sex? Animals are better because they can distinguish male from female," Pacquiao told a Philippine television broadcaster.

"If men mate with men and women with women they are worse than animals."

After the comments went viral on the internet the 37-year-old athlete, who is nearing the end of his boxing career, apologised in a Facebook video.

"Please forgive me for those I've hurt. God bless!" he said.

Pacquiao has reinvented himself as a conservative Bible-bearing politician as he campaigns for a seat in the Philippine senate at elections in May, only weeks after his last scheduled fight with Timothy Bradley in Las Vegas on April 9.

He is set to receive at least $US20 million ($28.20 million) for the fight.

Pacquiao is a hugely popular figure in the majority Catholic Philippines, with voter surveys showing he is among the strongest senate candidates.

He is currently a member of the House of Representatives but has rarely shown up for sittings.

Among those who lashed out at Pacquiao over the remarks was popular gay comedian and television host Jose Marie Viceral, known as Vice Ganda.

He said gays, lesbians, bisexuals and transgenders will pray for Pacquiao, who has brought his country honours.

Vice Ganda quoted Pope Francis saying "if a person is gay and he searches for the Lord and has good will, who am I to judge."

Danton Remoto, chairman of the LGBT group Ladlad suggested that Pacquiao and his advisers "bone up on LGBT issues" of the 21st century.

"Otherwise they will be left in the Dark Ages, when the cavemen ruled and the numskulls roamed the earth," he said.

More than 18,000 local, regional and national positions are up for grabs at the May election, including the presidency.

- with agencies