Aides have said in the past that Marcos had tested negative for cocaine and methamphetamine. When asked to respond to his elder sister’s allegations, the president briefly paused and then said in a televised news conference: “It’s anathema to talk about family matters generally in public. We do not like to show our dirty linen in public.”

The president suggested that something was troubling her sister. “The lady that you see talking on TV is not my sister and that view is shared by our cousins, friends, that it’s not her,” he said without elaborating.

“That’s why we are worried, we are very worried about her. I hope she feels better soon,” the president said. When asked if he plans to talk to her, Marcos said that he and his sister “no longer travel in the same circles, political or otherwise”.

Marcos, 68, and his sister are children of then dictator Ferdinand Marcos Snr, who was overthrown in an army-backed but largely peaceful “people power” uprising in 1986 after an authoritarian era that was notorious for human rights and political repression and plunder. The dictator died in exile in Hawaii in 1989. His family returned to the Philippines in 1991 and slowly regained a political foothold.