Canada's Prime Minister Justin Trudeau has apologised for doing "brownface" 18 years ago at an "Arabian nights"-themed party in a private school where he was a teacher.

The 2001 photo of Trudeau standing with four other women dressed in a white turban and robe, with his face, neck, and hands completely darkened, was first reported by Time.

The magazine obtained the photograph from a Vancouver businessman.

Trudeau has also admitted that this is his second instance of racist behaviour.

Previously in high school, he had put on make-up to sing Day-O (Banana Boat Song), a Jamaican folk song performed by African-American singer and civil rights activist Harry Belafonte.

The photo appeared one week into a federal election campaign with Trudeau's Liberal Party in a tight contest against the Conservatives led by Andrew Scheer.

Trudeau apologises, says he did not know it was racist at that time

Trudeau apologised on Sep. 18, following the publication of the photo by Time, Canadian Broadcasting Corporation reported.

Trudeau said: "In 2001, when I was a teacher in Vancouver, I attended a gala. The theme was Arabian Nights. I dressed up in an Aladdin costume and put makeup on. I shouldn't have done that. I should have known better, but I didn't and I'm really sorry."

Trudeau also admitted that he did not know it was racist at that time, and added that he took responsibility for his decision to dress up in this manner.

"I take responsibility for my decision to do that. I shouldn't have done it. I should have known better. It was something that I didn't think was racist at the time, but now I recognise it was something racist to do and I am deeply sorry."

When asked if he should resign as leader of the Canadian Liberal party over the incident, Trudeau said the incident should be treated on a "case-by-case" basis.

He said: "There are people who make mistakes in this life and you make decisions based on what they actually do, what they did and on a case-by-case basis. I deeply regret that I did that. I should have known better but I didn't."

Slammed by opposition as unfit for office

Trudeau has since come under fire from several quarters for his "brownface" stint, CBC further reported.

Scheer, the leader of the Canadian Conservative party, slammed Trudeau as unfit to govern the country.

Scheer said: "Wearing 'brownface' is an act of open mockery and racism. It was just as racist in 2001 as it is in 2019. And what Canadians saw this evening was someone with a complete lack of judgment and integrity and someone who is not fit to govern this country."

Jagmeet Singh, leader of the third-place New Democratic Party (NDP) condemned Trudeau's behaviour as "troubling" and "insulting", and that his actions were making a mockery of people's lived experiences.

Criticism also came from the National Council of Canadian Muslims (NCCM), who said that Trudeau's actions were "disgraceful, plain and simple."

Mustafa added: "Seeing the prime minister in brownface/ blackface is deeply saddening. The wearing of blackface/brownface is reprehensible, and hearkens back to a history of racism and an Orientalist mythology which is unacceptable."

The NCCM subsequently issued another statement thanking Trudeau for his apology on Twitter afterwards.

UPDATE: We thank the Prime Minister for his apology.

Prime Minister Trudeau's apology came less than an hour after NCCM called on him to apologize for wearing blackface/brownface.

Promises made, promises kept. That's the NCCM way.

— NCCM (@nccm) September 19, 2019

Photograph given to Time by Vancouver businessman

Time reported that the photo came from the 2000-2001 yearbook of West Point Grey Academy, and was given to the magazine by a Vancouver businessman named Michael Adamson, who was part of the West Point Grey Academy community.

Adamson himself was not at the party in 2001, which was attended by school staff and parents of students.

He added that he first saw the photograph in July and thought it should be made public.

Trudeau, king of multiculturalism

Trudeau has been hailed as the king of multiculturalism.

A fervent advocate of a multicultural Canada, which he said is integral to Canadian identity, half of Trudeau's Cabinet are women, and at least six members have Asian or African heritage.

While in Singapore in November 2018, Trudeau won praise for his social etiquette and respect for minorities:

He also won fans for his charming down-to-earth personality:

However, his administration in Canada has been plunged into controversy after accusations of political meddling in a bribery case against engineering giant SNC-Lavalin.

Two members of his own Cabinet accused him and his aides of meddling in the prosecution of SNC-Lavalin to save jobs.

The two members in the Cabinet were ministers.

One was a women and one was Canada's first indigenous attorney general.

They were expelled from the party.

Trudeau's great-great-great-great-grandmother was William Farquhar’s daughter.

Trudeau is the son of former prime minister Pierre Trudeau, who is considered the father of modern Canada.

Before becoming prime minister, the younger Trudeau worked as a teacher, snowboard instructor, a bartender and a bouncer.

Top photo by Time