Mulroney began working with Trudeau past year.
He added: "Why should I, as President of the United States, allow countries to continue to make Massive Trade Surpluses, as they have for decades, while our Farmers, Workers & Taxpayers have such a big and unfair price to pay?" Not long after Trump issued two tweets calling Trudeau "very dishonest & weak".
"I have made it very clear to the President that it is not something we relish doing, but it something that we absolutely will do", Trudeau said. -Canada trade dispute following the weekend's G7 summit.
Ms Bishop said the Turnbull government's strong relationship with the United States administration was behind Australia securing an exemption to USA import tariffs on steel and aluminium.
The summit was seen as an opportunity to overcome disagreements on new tariffs imposed by the United States on imports.
In particular, Canada, Japan and the European G7 powers are outraged by Trump's unilateral - or illegal, in their eyes - the imposition of tariffs on imported steel and aluminium in the name of preserving U.S. industry on national security grounds. Pre-summit reports from the White House suggested that the president even considered skipping the summit altogether.
Trump's actions are being called ludicrous and absurd - but then again, coming from a man whose only experience before entering politics was as a businessman (with highly questionable dealings and tactics) and a reality TV show host, might not be all that surprising.
"The Prime Minister said nothing he hasn't said before - both in public, and in private conversations with the President", the statement read. "We just shook hands!"
Peter Navarro says his job was to send a "signal of strength" after Trudeau's post-G7 news conference sent the US president into a fit of pique that threw the summit into disarray.
As might be expected, Trudeau's foreign minister Chrystia Freeland took his side.
Mr Trudeau and the European Union have vowed to take retaliatory action next month over U.S. tariffs on steel and aluminum.
Senior officials of the Trump administration piled on the smears.
"He really stabbed us in the back. This I've never seen before, nor has anyone else", Mulroney said.
Foreign Affairs Minister Chrystia Freeland first announced "dollar-for-dollar tariffs" against the USA on May 31.
Trudeau was away from the House of Commons on a "personal" day on Monday. According to a Canada release, they make nearly 100 Billion Dollars in Trade with USA (guess they were bragging and got caught!).
The verbal volleys by Mr Navarro and Mr Trump's top economic adviser, Larry Kudlow, picked up where Mr Trump left off on Saturday evening with a series of tweets from Air Force One en route to Singapore for his nuclear summit on Tuesday with North Korea's Kim Jong Un.