Prime Minister Justin Trudeau has apologized for a "lack of respect" he showed towards a protester who confronted him about mercury contamination in a First Nation community during a Liberal fundraiser in Toronto.

During a media scrum in Halifax on Thursday morning, Trudeau said he always tries to be respectful and to engage with protesters in a "positive" way, but admitted he didn't do that the night before.

"Last night I lacked respect towards them and I apologize for that," he said.

On Wednesday night, hecklers at a fundraiser, organized by the Laurier Club that requires a minimum contribution of $1,500 to join, called out Trudeau's handling of mercury poisoning on the Grassy Narrows First Nation. In response, he thanked them for contributing to his party’s coffers.

"Thank you very much for your donation tonight, I really appreciate the donation to the Liberal Party of Canada," Trudeau said to cheers from the crowd.

Trudeau said Thursday he plans to refund the protesters’ donations.

"Obviously we will be fully refunding the contributions made by those individuals last night," he told reporters. "They wanted to express their concerns about an issue, and I do take that seriously."

A Twitter account that appears to be run by the protesters posted a video of the interaction and accused Trudeau of "failing to help" Grassy Narrows. The account also reacted to Trudeau's comments, tweeting "smugger words have never been said."

Judy Da Silva, the environmental health co-ordinator for the Grassy Narrows First Nation, called the remark "callous."

"He could have treated us in a humane way and asked the lady – no I want to hear her, bring her back, I want to hear her question. He could have said that. But instead he just made fun of her," Da Silva said in an interview with host Glen McGregor on CTV’s Power Play Thursday.

"I don’t feel that the word reconcile should exist anymore."

Grassy Narrows suffers decades of mercury poisoning

The issue plastered across the large banner a protestor wielded at Trudeau's fundraiser Wednesday night was the mercury poisoning that continues to ravage Grassy Narrows First Nation.

The community, which sits near Ontario's border with Manitoba, has been struggling with the effects of a chemical plant dumping waste mercury in its local river in the 1960s and 1970s. Mercury poisoning can result in impaired cognitive functions and issues with speech, vision and hearing. It also causes weakness in the muscles as well as numbness and tingling in the mouth and extremities.

With prolonged exposure, the damage can become irreversible.

Grassy Narrows residents have been pushing the government to move forward on its pledge to build a treatment centre in the community for those suffering from mercury poisoning. Then-Indigenous Services Minister Jane Philpott first made the pledge in late 2017, but the community is still waiting for the dedicated treatment centre.

Trudeau told reporters on Thursday that his office will be speaking with Indigenous Services Minister Seamus O’Regan's office to make sure the government is looking at "everything" they can do to "continue to work hard in resolving this situation."

"The situation in Grassy Narrows is one that we have been following for quite a while. It involves elements of provincial jurisdiction and federal responsibility," Trudeau said.

However, Da Silva said Trudeau's remarks on Wednesday evening made her feel less optimistic about the government’s commitment to addressing the mercury poisoning issue.

"With last night's reaction at the Trudeau fundraiser…I felt like things aren’t going to happen," Da Silva said, "he's not fulfilling that commitment to protect our people."

Trudeau blasted for Grassy Narrows comments

Trudeau came under heavy fire from politicians and advocates alike after his comments and the Liberal fundraiser Wednesday night.

NDP Leader Jagmeet Singh said Trudeau’s comments were a "sad example" of the "colonial disregard for Indigenous lives" that he says contributed to the suffering in Grassy Narrows.

"Instead of showing respect for people fighting for clean water [and] funding, Trudeau sides with his rich donors to get a laugh," Singh tweeted.

Conservative Deputy Leader Lisa Raitt also weighed in.

"That snarky comment by the PM to the young female protester is just ignorant. 'Thanks for your donation'. Way to go Bro," she tweeted.

Conservative MP Michelle Rempel also called Trudeau "smug" and "arrogant."

The Assembly of First Nations' National Chief Perry Bellegarde called on Trudeau to apologize directly to those involved. Bellegarde also said Trudeau should visit Grassy Narrows and the neighboring Wabaseemoong, which are still being impacted by mercury poisoning.

"PM's comments are unacceptable and offensive," Bellegarde wrote in a tweet. "Above all, it’s time for action for children and families in these First Nations."

With files from CTV's Jackie Dunham.