The 'All of Me' hitmaker has been a vocal critic of the US leader and he insists he is right to use his public platform to condemn the political landscape because the former 'Apprentice' star ''deserves'' it.
He said: ''He deserves the criticism. He's done some awful things, and I think he's a really terrible person as well.
''I think he's selfish, he's racist, he's misogynist, he's a liar, probably the worst liar we've even seen in public life, really ill-informed, a narcissist... I could go on!
''But I think it's clear he's an awful person and shouldn't be president.''
The 39-year-old singer has crossed paths with his friend Kanye West over their differing attitudes towards the president and he's urged the 'All Day' rapper to take a closer look at Trump's policies and how they affect people.
Speaking on UK TV show 'This Morning', he said: ''It's not an uncommon thing for people to disagree politically... but I'm right and he's wrong!
''And what I was pointed out [to Kanye] is that it doesn't matter if you like this guy personally, what matters is what he's doing in office.
''One of the things he's chosen to do is use the office as a tool... to say we don't want certain immigrants to come from certain countries because they don't look a certain way, treating immigrants like they are animals, separating their families...
''And if you put his policies into action they cause real life consequences for people, and they are pretty awful.''
John - who has children Luna, two, and Miles, three months, with wife Chrissy Teigen - admitted he wishes he could do more to instigate change.
He said: ''In my new song, I say you can't preach you have to do something. It's frustrating... you can vote, but hopefully, congress and other officials will respond and hold him accountable.''
However, he has no plans to run for office himself.
Asked if he'd run for president, he said: ''No! But I believe we should stay engaged and be a part of politics.''
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