Speaking at The Irishman's European premiere at the BFI London Film Festival's closing night gala, the 76-year-old told Sky News: "Trump is a monster. He's a monster without even realising it, he's just too stupid to realise.

"He said there's a famous quote somewhere about the mundaneness and banality of evil... And he is too stupid to even know he's evil.

"He allows evil to come around him and use him, he might not initiate something evil, but he will allow it.

"We will have a problem with him if we don't get rid of him."

De Niro is a vocal critic of the US president and has previously said he would like to see him go to jail.

Mr Trump is currently facing an impeachment inquiry led by Democrats on Capitol Hill.

Sky News