Trump lashed out at Trudeau after the G7 issued a joint communique on Saturday in which the embattled alliance managed to overcome some differences and find areas of common ground.
After his meeting with the North Korean leader, Trump praised the Kim, which stood in contrast to some of his harsher words over the past few days about Trudeau.
Navarro also said Trudeau is "weak and dishonest".
Trudeau said in a press conference that Canada will "move forward with retaliatory measures on July 1, applying equivalent tariffs to the ones that Americans have unjustly applied to us".
Note that Navarro expressed regret only for the language, not the message, which is that Trudeau had better show President Trump more deference in the future.
Earlier on Tuesday at the Washington conference, White House Council of Economic Advisers Chairman Kevin Hassett said the US and Canada need to "take a deep breath". "He learned", Mr Trump said, wagging his finger.
In response to Trump's tweets, the PMO released a statement shortly after that simply read, "The Prime Minister said nothing he hasn't before - both in public, and in private conversations with the President".
On Monday, MPs in the House of Commons approved a motion denouncing Trump's name-calling tirade and endorsing Trudeau's decision to stand his ground against US tariffs and tweeted presidential threats. The US president and Mr Trudeau have had a friendly relationship in the past, but tensions over US tariffs have strained the diplomatic partnership.
He also justified the newly imposed tariffs on Mexico, Canada and the European Union citing national security concerns, which their oldest ally has evidently found to be "insulting".
"That's going to cost a lot of money for the people of Canada", Trump said in Singapore. And I say, 'Push him around? "We just shook hands!"' Trump said.
International Trade Minister Francois-Philippe Champagne echoed that sentiment, saying, "We'll continue to do diplomacy the Canadian way, which is to be positive, to be constructive and to make sure we are firm to defend our industries and our workers".