Cher has startled attendees at a world youth summit in Ottawa delivering a scathing and sometimes profane denunciation of the Republican candidate Donald Trump, saying she feels “traumatised” by him and it would be millennials who would be most harmed if he is elected.

“I’m trying to parse my words…I’m not good at it, he’s an asshole,” the actress and singer said while in discussion on the main stage at the four-day One Young World Summit, where speakers this week also included Sir Bob Geldof and former UN Secretary General, Kofi Annan.

“What he’s awakened in my country is bigotry and distrust and a certain kind of supremacy in certain groups,” Cher, who started her career in the 1960s as one half of Sonny and Cher, declared, adding that should he win the repercussions would be felt around the world.

“What they need to know is that this election will change America and have consequences for the world for 40 years and the people who will suffer the most are millennials,” she said. “Look, it’s not going to hurt me, I’m 70, it’s not going to do anything to me. It’s going to do stuff to young people and that really scares me and it bothers me.”

“He’s so terrific at lying,” she offered. “I’ve never seen anyone so good, it’s amazing. I could go on and on, on this subject forever because I’m so traumatised by him. I am truly traumatised by him.”

She said that Ms Clinton is in a close fight with him in part because millennials are not embracing her. “They’re not drawn to Hillary; they don’t trust her, they feel that her sins are really enormous,” she said, adding that they need to look more closely and not take their news in soundbites. “They’re just hearing that and that and that.”

“I know a different side of her, I know the really warm side of her,” she said.

Sometimes called the ‘Goddess of Pop’, Cher was invited to the annual summit, which brings promising young leaders from around the world to share experiences and visions, as one of its keynote speakers. Also given the microphone was Canadian Prime Minster, Justin Trudeau.

“I do not think you are the leaders of tomorrow - I know you are already leaders today,” Mr Trudeau, 44, told participants. “Your generation is politically engaged, educated, innovative, inclusive and progressive. You need to harness that potential to make the world a better place and I know that every person here tonight is committed to doing just that in one way or another.”

Cher warned that a Trump presidency would roll back progress in the US on social policies ranging from abortion to gay rights.