President Rodrigo Duterte on Thursday landed an insulting verbal blow on boxing superstar Manny Pacquiao, seen as a possible successor in next year's presidential election.
Pacquiao has recently railed at corruption in government as well as the president's friendly relationship with China.
"When you are a champion in boxing, it does not mean to say that you are a champion in politics," Duterte told a media briefing. "He is blubbering his mouth."
Pacquiao, 42, had long been among Duterte's strongest supporters, but is seen as a possible contender when Duterte's single six-year term ends.
Duterte asked why the boxer-turned-lawmaker was only talking about corruption now - and said he should focus on investigating graft rather than leaving the country to prepare for a fight next month.
"I would say that you are shit," Duterte said. "Start investigating. Comply first with your duty as senator. Don't be absent."
Pacquiao's office said he would respond at a news conference on Saturday. He and Duterte belong to the same political party, which is urging the president to run for vice president next year.