A Montreal NDP candidate has resigned after being accused of domestic abuse against his former spouse on social media.

Olivier Mathieu was the nominee for the LaSalle-Émard-Verdun riding in the southwest of Montreal.

On Wednesday, he posted a statement on the riding's Facebook page, denying any wrongdoing.

"It is with a very, very heavy heart that I must announce my withdrawal," Mathieu wrote. "This morning, a person made serious accusations against me on social networks.

"What has been said about me is false, and I intend to prove it. But in the current context, it is important to me, first and foremost, that the energies of the NDP are entirely dedicated to presenting our platform," the statement adds.

"In the coming weeks, months, I will take the necessary steps to clear my reputation of any suspicion."

In an interview with CBC News, his former wife, Rebecca Stuart, alleged he was physically abusive during six years of their seven-year relationship.

"He slapped, hit me with the back of his hand and split my lip open. I had to go to the ER and have emergency plastic surgery on my lip," she told CBC. "One night, he slapped me across the side of my face, burst my eardrum."

She sent an email outlining the same information to NDP Leader Jagmeet Singh on Sept. 10. She did not receive a response.

Her allegations have not been tested in court, but CBC spoke with two of Stuart's friends. One confirmed that he had knowledge of the alleged abuses at the time. The other said she regularly witnessed Stuart with unexplained injuries.

CBC has confirmed the pair were previously married and divorced in 2015.

Information sent to party

When Stuart saw that he was running for election, she said she had a visceral reaction.

"It made me feel sick. It made me feel sick to my stomach when I saw it," she said.

She posted the allegations on her own social media, tagging the riding's Facebook page, Jagmeet Singh's Facebook page and the national NDP Facebook page.

She also posted it directly on the local riding's Facebook page, but claims it was removed. She provided CBC News with a screenshot of the post.

CBC News contacted the NDP to ask about the allegations, and attempted to contact Mathieu directly. Shortly after, the party responded, saying Mathieu had "decided to step down."

"We learned recently about serious allegations against a candidate. We accept his resignation as it's clear, with these allegations, he could not go on as a candidate for our party," the NDP said in a statement.

Stuart says she's thankful the response was swift.

"Honestly, I'm happy it didn't take more than what's happened so far for them to realize that maybe it was a questionable decision," Stuart said.

NDP has strong vetting process, Singh says

Singh commented on the NDP's recruitment practices as he spoke on the campaign trail to media in Brampton, Ont., saying Thursday that the party has a strong vetting process in place.

When the party receives the information that a candidate is not meeting "the standards that we believe [are] important for our candidates to meet," that person can no longer represent the NDP, he said.

"I'm confident that people can trust us to know that we're making good decisions about the candidates we have. There is a high quality standard that we're trying to achieve."