Fredericton MP Jenica Atwin is poised to bolt from the Green party caucus today and cross the floor to join the governing Liberals, CBC News has learned.

Atwin is expected to make the announcement at a news conference in Fredericton later today, with Intergovernmental Affairs Minister Dominic Leblanc by her side.

A senior Liberal source said Atwin initiated the floor-crossing several weeks ago when she reached out to the governing party.

The source said Atwin expressed comfort with the Liberals' approach to core issues such as the environment and reconciliation. Atwin's husband Chris Atwin is a councillor with the Oromocto First Nation.

Atwin accomplished a historic breakthrough for the Greens in the last election — winning their first ever seat in Atlantic Canada when she defeated Liberal incumbent Matt DeCourcey in Fredericton. Atwin, along with Paul Manly and former leader Elizabeth May, gave the Greens three MPs and their largest caucus in history.

A fracture over the Middle East

Atwin's departure comes after the Israeli-Palestinian conflict exposed fault lines in the Green party ranks.

Atwin directly challenged party leader Annamie Paul's position on the conflict, saying Paul's call for de-escalation and a return to dialogue between the two was "totally inadequate."

"I stand with Palestine and condemn the unthinkable airstrikes in Gaza. End Apartheid!" Atwin tweeted on May 11.

The day before, Manly tweeted that the removal of Palestinian families from the East Jerusalem neighbourhood of Sheikh Jarrah "is ethnic cleansing."

More recently, the Canadian Press reported that the Green executive committee voted not to renew the contract of one of Paul's senior advisers.

The adviser, Noah Zatzman, had expressed solidarity with Israel in a May 14 social media post that accused many politicians, including unspecified Green MPs, of discrimination and antisemitism, sparking a letter-writing campaign calling for his removal.

Separately, two party executives recently announced they would step down early. One of them was John Kidder, a vice-president on the party's governing body and husband to MP and former leader Elizabeth May.

In the 2019 campaign, Atwin said left-leaning voters felt "betrayed" when Trudeau broke a promise to reform the electoral system and said they were now looking at the Greens as a more genuine progressive choice.

"We think we're that option," she said. "We think we're the ones to look to for voters looking for change, and looking to get better outcomes than what we've seen in the last four years."

She also accused Trudeau of "fear-mongering" when he warned voters that a Liberal-Green vote split would help elect a federal Conservative government.

But she welcomed his promise during that campaign to pressure the New Brunswick provincial government of Premier Blaine Higgs to fund abortions at Fredericton's Clinic 554.

"It is interesting that he hasn't brought it up before, but support is support," she said at the time. "I want to see Clinic 554 stay open ... so I appreciate that he's now stepping forward. It would have been nice to see during the Gallant government as well."