The former Philippine president Rodrigo Duterte accused his successor, Ferdinand Marcos Jr, of being a drug addict who risked being ousted from office in an expletive-laden tirade that underlined the breakdown in relations between the two powerful political families. Duterte’s speech on Sunday, in which he claimed Marcos Jr’s allies were trying to remove constitutional term limits so they could cling to power, follows long-running speculation about hostilities between the families. Duterte’s daughter Sara Duterte ran on a joint ticket with Marcos Jr in the 2022 election, winning a landslide victory, and is now his vice-president. However, cracks have since emerged in their alliance. Marcos Jr told reporters on Monday: “I think it’s the fentanyl,” when asked about Duterte’s remarks, suggesting the drug – which Duterte has admitted taking in the past for pain relief after a motorbike accident – had impaired his judgment. He added that the former president “has been taking the drug for a very long time now ... after five, six years, it has to affect him.” During his speech, Duterte warned Marcos Jr against pursuing any changes to the constitution, warning he could be ousted like his father. Marcos Jr’s father, the late dictator Ferdinand Marcos Sr, ruled the Philippines for more than two decades until he was unseated by the peaceful People Power Revolution in February 1986. The Marcos family was forced to flee the country, and sought exile in Hawaii. The 1987 constitution, which came into force a year after Marcos Sr was ousted, says presidents can only serve a single six-year term, as a safeguard against dictatorships. Marcos Jr has backed changes to the constitution to allow the promotion of foreign investment. However, Duterte claimed the president’s allies were bribing local officials to remove term limit rules. He did not provide any evidence to support his claim. Duterte also repeatedly accused Marcos Jr, who is known as Bongbong, of drug use, saying: “Bongbong Marcos was high back then. Now that he’s the president, he’s still high … We have a drug addict for a president! That son of a whore!” according to comments reported by the news site Rappler. Duterte said Marcos Jr’s name was included on a list produced by the Philippine drug enforcement agency. The agency has denied this. Duterte, who was blocked by the constitution from seeking a second term in 2022, has always had an uneasy relationship with Marcos Jr, and previously called him a spoiled child and weak leader. He did not endorse him in the last election, and openly expressed frustration that his daughter did not go for the top job. There is widespread speculation that Sara Duterte will contest the 2028 presidential race, however, placing the two families on a collision course. Marcos Jr has pursued a different foreign policy to Duterte, taking a tougher stance against China in the disputed South China Sea and strengthening ties with the US. Relations between the families have also been strained by reports that investigators from the international criminal court, which is investigating Duterte’s brutal drugs crackdowns, visited the Philippines in December. The reports have not been confirmed, and Marcos Jr has said he will not cooperate with the court. On Sunday, Duterte’s son and Davao City mayor , called for Marcos Jr’s resignation, suggesting he was pursuing a dangerous foreign policy and was responsible for rising criminality. “Mr President, if you do not have love and aspirations for your country, resign,” he said at a public forum event. Sara Duterte said on Monday that her brother’s comments came from “a place of brotherly love” and alleged she was being subject to “despicable treatment” by “some sectors within the circle of the president”.