Justin Trudeau said the diversity of Canada is oe of their greatest strengths. (File)

Canadian Prime Minister Justin Trudeau on Monday added his voice to those condemning an attack by U.S. President Donald Trump against four minority Democratic congresswomen, saying "that is not how we do things in Canada."

Trump on Monday defended his comments, saying he was not concerned if people thought his tweets were racist. The four hated the United States, he told reporters.

"I think Canadians and indeed people around the world know exactly what I think about those particular comments. That is not how we do things in Canada," Trudeau told a televised news conference in Petawawa, Ontario.

"A Canadian is a Canadian is a Canadian, and the diversity of our country is in fact one of our greatest strengths ... and we will continue to defend that."

Canada, a country of 36 million, has traditionally prided itself on being one of the most diverse nations on earth. Every year it sets immigration targets approximating to roughly 1% percent of the population.

Earlier in the day, a British government spokesman said Prime Minister Theresa May felt Trump's language in the tweets was "completely unacceptable".

Trudeau's relations with Trump have improved steadily since June 2018, when the U.S. president called him "very dishonest and weak." Last month the two men held what Canadians officials described as positive meeting in the White House.