Barack Obama has voiced support for Canada's embattled Prime Minister Justin Trudeau, who just last month was at the center of a racism row when three photos emerged of him in blackface.

Obama's encouraging words were issued in a tweet on Wednesday ahead of Canada's federal election next week, in which Liberal Trudeau is widely tipped to be defeated by the Conservatives following the succession of scandals.

'I was proud to work with Justin Trudeau as President. He's a hard-working, effective leader who takes on big issues like climate change,' Obama declared on Twitter this afternoon. 'The world needs his progressive leadership now, and I hope our neighbors to the north support him for another term.'

Former president Barack Obama has voiced support for Canada's embattled Prime Minister Justin Trudeau, who just last month was at the center of racism row when three photos emerged of him in blackface

Obama's encouraging words were issued in a tweet on Wednesday ahead of Canada's federal election next week, in which Liberal Trudeau is largely tipped to be defeated by the conservatives following the succession of scandals

Elected in 2015, Trudeau, 47, worked alongside Obama during his final months in office, and, during that time, the pair developed a strong working relationship regularly referred to as a 'bromance'.

But Trudeau's reputation as a progressive politician took a huge blow last month when three historical images of the Liberal Leader in blackface emerged in the press.

Hours after he apologized for wearing brown make-up on his face, neck and hands while wearing a turban and robe at an Arabian Nights gala in 2001, two more images surfaced depicting similar offensive scenes.

In the first of the two images, Trudeau is dressed up as Jamaican singer Harry Belafonte to sing Day-O, a Jamaican song, at Jean Brebeuf High School at a talent show in the early 1990s.

The second is taken from a video which is undated but shows him with a black face and raising his arms and sticking his tongue out while dressed in a white t-shirt and jeans.

Trudeau issued a second apology for the two additional images, saying that though he did not remember the third incident, he understood it was 'unacceptable' and that he has enjoyed 'layers of privilege' in his life.

Elected in 2015, Trudeau, 47, worked alongside Obama for his final months in office. During that time the pair developed a strong working relationship and have remained friendly ever since, regularly publicizing their social outings together and documenting their 'bromance'

A yearbook photo emerged last month showing Canada's Prime Minister Justin Trudeau wearing brownface to a party 18 years ago when he was a private school teacher in Vancouver

Trudeau also dressed up as Harry Belafonte in the 1980s (left) and again in the 1990s (right)

He asked for forgiveness but would not confirm that those three incidents were the only times in his life he had worn blackface, staying silent when a reporter yelled out to ask if any additional photos would emerge.

'What I did hurt them, hurt people who shouldn't have to face intolerance and bigotry because of their identity.

'This is something that I deeply, deeply regret,' Trudeau said.

'Darkening your face, regardless of the context or the circumstances, is always unacceptable because of the racist history of blackface.

'I should have understood that then and I never should have done it,' he said.

Despite his pleas for forgiveness, support for the Prime Minister plummeted in the days afterward, with a Nanos research poll released late last month suggesting Trudeau's conservative rivals would win 35.5 per cent of the national vote and the Liberals 32.9 per cent.

The turbulence didn't ended there for Trudeau either. He was forced to appear wearing an armored vest accompanied by a heavy security detail at an election rally in Ontario on Saturday, following an 'unspecified threat'.

Officials would not reveal the nature of the threat, but it resulted in a 90-minute delay before Trudeau appeared before 2,000 supporters who had turned out as the election campaign ahead of the October 21 vote.

Trudeau wore a suit jacket rather than his usual rolled-up sleeves and loosened tie, and was wearing a vest, which was noticeable in photos taken at the event.

He was escorted through crowd by a large number of plainclothes Royal Canadian Mounted Police officers as well as Mounties dressed in green tactical gear.

Justin Trudeau wore a suit jacket rather than his usual rolled-up sleeves and loosened tie, and was wearing a vest, which was noticeable in photos taken at the event in Ontario where he appeared in front of around 2,000 supporters

Officials did not reveal what the nature of the threat was, but there was a heavy police presence surrounding the Canadian PM

Obama's endorsement will be seen as a welcome message for Liberals, coming just hours after Trudeau conceded the Conservatives could win Monday's election, accusing them of running one of the 'dirtiest, nastiest' election campaigns in Canadian history'.

'We know that the Conservative Party is running one of the dirtiest, nastiest campaigns based on disinformation that we've ever seen in this country,' Trudeau said in a press conference.

'And it's no surprise that they don't want to share whose deep pockets are funding their attacks on Canadians, on other parties and on the most important fight of our generation, the fight against climate change.'

Trudeau has not yet responded to Obama's words of support, however the tweet did illicit a response from a spokesperson for President Trump's 2020 reelection campaign, calling the message 'foreign election interference.'

Liberal Party spokesperson Zita Astravas told CTV the Liberal Party did not pay or request the endorsement.