The United States and Canada are facing a diplomatic and trade crisis as top White House advisers hurled insults at Canadian Prime Minister Justin Trudeau on Monday morning, accusing him of “stabbing the US in the back”.

US President Donald Trump called Mr Trudeau “very dishonest and weak” after leaving the Group of Seven heads of government meeting in Canada on Sunday, shattering any hope its northern neighbour could avoid US tariffs on steel and aluminium, or renegotiate the North American Free Trade Agreement.

White House economic adviser Larry Kudlow and trade adviser Peter Navarro drove the message home in an extraordinary assault on a close US ally and neighbour.

Mr Kudlow accused the Canadian PM of betraying Mr Trump with “polarising” statements on trade policy that risked making the US leader look weak ahead of a historic summit with North Korean leader Kim Jong-un.

“[Trudeau] really kind of stabbed us in the back,” Mr Kudlow, the director of the National Economic Council, who accompanied Mr Trump to the G7 summit said on Monday morning on CNN.

Mr Navarro told Fox News: “There is a special place in hell for any leader that engages in bad faith diplomacy with President Donald J. Trump and then tries to stab him in the back on the way out the door and that’s what bad-faith Justin Trudeau did with that stunt press conference. That’s what weak, dishonest Justin Trudeau did.”

Peter Navarro: "There's a special place in hell for any foreign leader that engages in bad faith diplomacy with President Donald J. Trump." https://t.co/fxgY5mfAY1 pic.twitter.com/ddcSu0TMd8

— Fox News (@FoxNews) June 10, 2018

The spat has also drawn in Germany and France, which sharply criticised Mr Trump’s decision to abruptly withdraw his support for a G7 communique hammered out at a Canadian summit, accusing him of destroying trust and acting inconsistently.

President Emmanuel Macron reacted with a statement slamming Mr Trump’s behaviour at the summit.

“International co-operation cannot be dictated by fits of anger and throwaway remarks,” he said in a statement.

“We spend two days working out a [joint] statement and commitments. We are sticking to them and whoever reneges on them is showing incoherence and inconsistency.

“Let’s be serious and worthy of our people. We make commitments and keep them.”

Canadian Foreign Minister Chrystia Freeland had responded to the White House comments by saying that Canada will retaliate to US tariffs in a measured and reciprocal way and that Canada will always be willing to talk.

“Canada does not conduct its diplomacy through ad hominem attacks … and we refrain particularly from ad hominem attacks when it comes from a close ally,” Ms Freeland told reporters in Quebec City on Sunday.

Mr Trudeau, in Quebec City for bilateral meetings with non-G7 leaders after the summit, did not respond to reporters’ questions as he arrived, but his office pointed to Ms Freeland as the minister responsible for Canada-US relations.

When Mr Trump’s tweets withdrawing support from the G7 statement hit on Sunday, the Prime Minister’s office said Mr Trudeau had not said anything in his closing news conference he has not said to the US President before.

PM Justin Trudeau of Canada acted so meek and mild during our @G7 meetings only to give a news conference after I left saying that, “US Tariffs were kind of insulting” and he “will not be pushed around.” Very dishonest & weak. Our Tariffs are in response to his of 270% on dairy!

— Donald J. Trump (@realDonaldTrump) June 9, 2018

Ms Freeland told reporters that she had met US Trade Representative Robert Lighthizer on Friday and would speak to him later on Sunday, adding that she believes a deal to renew the North American Free Trade Agreement is still possible.

“We are convinced that a modernisation is perfectly possible. We are convinced that common sense will triumph,” she said.

Some 75 per cent of Canadian exports go to the US, making Canada uniquely vulnerable to a US trade war.

-with AAP