Canadian Prime Minister Justin Trudeau has admitted he made a joke about Donald Trump to other world leaders in a hot mic incident.

Mr Trudeau came clean during a Q and A in London after the US President called him two-faced over his comments and decided to cancel a press conference following the NATO meeting on Wednesday.

The Canadian leader said he reacted because he was surprised by the length of the US President’s media session on Tuesday.

Mr Trudeau said: “Last night I made a reference to the fact there was an unscheduled press conference before my meeting with President Trump, I was happy to take part in it but it was certainly notable.

“We were all surprised and I think pleased to learn that the next G7 will be at Camp David, I think that was an unscheduled announcement and … I think every different leader has teams who every now and then their jaws drop at unscheduled surprises, like that video itself for example.”

US President Donald Trump (L) and Canadian Prime Minister Justin Trudeau arrive for a NATO leaders meeting at The Grove hotel and resort in Watford, England (Picture: AP)

US President Donald Trump (L) and Canadian Prime Minister Justin Trudeau arrive for a NATO leaders meeting at The Grove hotel and resort in Watford, England (Picture: AP)

Mr Trudeau also stressed he had a great relationship with Mr Trump and they had a great meeting.

Mr Trump called his Canadian counterpart “two-faced” when he was asked about the video filmed at the  Buckingham Palace reception on Tuesday evening.

During the casual chat, Boris Johnson can be heard asking French President Emmanuel Macron, who had a bilateral meeting with Mr Trump: “Is that why you were late?”

Donald Trump was not happy with the Canadian President (Picture: AP)

Donald Trump was not happy with the Canadian President (Picture: AP)

Canadian prime minister Justin Trudeau says: “He was late because he takes a 40-minute press conference off the top.”

Later in the conversation, Mr Trudeau adds: “You just watched his team’s jaws drop to the floor.”

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Mr Johnson called the video “complete nonsense” when he was asked about it later.

But Mr Trump didn’t hold back and said of Mr Trudeau: "He's two-faced... I find him to be a nice guy, but the truth is I called him out on the fact that he's not paying 2% [of national GDP towards defence] and I guess he's not very happy about it.