The 76-year-old singer is a vocal critic of the US leader and thinks the only thing the former 'Apprentice' star is good at is ''marketing'' and selling himself.
She ranted: ''I can't bear the man! He's a man with no manners! He doesn't see his own flaws; he doesn't know what he doesn't know. You know? He has no humility.
''He's good at marketing. He knows how to sell; he's a conman. That's what he's good at. But he doesn't think he needs anyone's help, he thinks he can go it alone.''
Barbra's feelings towards the president have influenced her new album, 'Walls', but she was careful not to mention him by name so as not to alienate listeners.
She explained in an interview with The Guardian newspaper: ''You have to write lyrics that can be more than just a protest.
''They have to appeal to a universal audience. Even when I wrote 'Don't Lie to Me', at first I thought, well, I could make you think it's like a love affair, a marriage breaking up. It's a universal thought: don't lie to me.''
The 'Star is Born' actress went on to accuse the US leader of ''reversing reality'' and branded him ''stupid'' and ''ill informed''.
She said: ''What [Trump is] doing is reversing reality, actually. It's like that joke: a woman walks in and her husband is in bed with another woman. And he says, 'Who are you going to believe, me or your lyin' eyes?'
''Facts matter. Words have meaning. This man defies that. He says climate change is a hoax. Let's release more coal and carbon into the air and have more megafires and hurricanes.
''I mean he's so stupid! He's so ill informed. Liar is not enough of a word. There must be a bigger word for someone who lies about everything.''
The 72-year-old president is known for hitting out at his critics on Twitter but Barbra doesn't care if she's his next target.
She said: ''I know that's a possibility. Maybe he doesn't think I'm powerful enough. I've seen him in the film of people in my audience ... maybe he's a big fan!
''I don't know. That's the chance you take. Whatever. The country is more important to me at this point than whether my album sells.
''I'm sure 'Don't Lie to Me' turns off a lot of people who are Republicans or rightwingers. But there are some good Republicans!''
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