Conservative Leader Erin O'Toole is warning his MPs that they risk the same fate as a senator expelled from the party caucus if they challenge his leadership.

O'Toole laid down the law Wednesday as he headed into a two-day Tory caucus retreat, one day after showing Sen. Denise Batters the door.

"You don't want to make that decision, but really, she made it for herself," he told reporters as he arrived for the meeting, flanked by members of his leadership circle.

"People that are now allowing their frustrations and their own personal agendas or issues on the pandemic to interfere with our progress are not part of the team."

He argued that the Conservative caucus needs to keep focused on defeating Prime Minister Justin Trudeau and holding his Liberal minority government to account. He added that anyone "who's not putting the team and the country first will not be part of this team."

Expelling Batters is the most serious consequence O'Toole has meted out for any member since his Sept. 20 election loss, which has triggered grumblings over his performance and internal struggles over the Conservatives' stance on vaccine mandates.

The Saskatchewan senator and longtime party stalwart launched a petition Monday aimed at forcing a referendum on O'Toole's leadership within the next six months, instead of waiting for a scheduled leadership confidence vote at the party's national convention in 2023.

As of late Wednesday, her office said the petition had garnered around 3,700 signatures. The party, however, has dismissed Batters' petition as an invalid way to trigger a leadership review — something she and her supporters reject.

In launching the petition, Batters, who was appointed to the Senate on the advice of former Conservative prime minister Stephen Harper in 2013, argued that O'Toole lost the election because Canadians didn't trust him. Having reversed his positions on a firearms ban, carbon taxes and conscience rights,she predicted he would be unable to win back voters' trust in future.

O'Toole warns more expulsions in store for any MP who challenges his leadership. #CPC #CDNPoli

Batters was unrepentant Wednesday.

"I am and will always be a Conservative," she said in a statement.

"It is ironic that Erin O’Toole is expelling me from our national Conservative caucus for asking him to adhere to the principles and policies our Conservative party members have approved."

She also questioned why she's being singled out when Sen. Michael MacDonald urged Tory MPs last month to give themselves the power to hold an early leadership review.

"If Mr. O’Toole is certain that the members of our party support the new direction in which he is taking our party, he should have nothing to fear by facing our members democratically in an expedited confidence vote," said Batters.

In a previous interview with The Canadian Press after her petition was launched, Batters said other MPs and senators support her efforts.

However, O'Toole insisted Wednesday his caucus is "united on our way forward." His team also believes it has the support of a majority of MPs to kick out any MP who publicly supports the effort by Batters oust O'Toole.

O'Toole can unilaterally expel a senator from the caucus but removal of an elected member would require a majority vote by MPs.

The leader last week pointedly left out of his shadow cabinet a number of MPs who've objected to mandatory vaccination against COVID-19 or questioned the efficacy of vaccines.

Among those was Leslyn Lewis, a newly elected representative for Ontario, who was heavily backed during last year's leadership race by the party's western and social conservative base. O'Toole had courted that bloc of supporters during the contest, billing himself as the 'true blue' candidate to party faithful.

Lewis has previously voiced support for O'Toole following the election loss, but a spokesperson for her office declined Wednesday to offer comment on Batters' petition.

Many MPs who were chosen for critic roles were quick to publicly denounced the senator on Monday and echoed that sentiment as they headed into Wednesday's caucus meeting.

Newly elected Ontario MP Michelle Ferreri said Batters should have kept her concerns behind the closed doors of caucus.

"I think Denise made her choices and I think we've got to focus on what Canadians need and get back to work," said Scott Aitchison, MP for Parry Sound—Muskoka.

Winnipeg MP Marty Morantz said he supports O'Toole's decision to remove Batters and the grassroots will get to have their say when the scheduled convention rolls around in two years.

"Mr. O'Toole's only been leader for just over 14 months. The members just had their say and I don't think it's productive at all to be taking leaders out after 14 months of being leader without giving Canadians an opportunity to get to know them and trust them."

While caucus appeared supportive of O'Toole's decision to expel Batters, her petition remains active. It is being promoted by groups representing swaths of the Conservative grassroots dissatisfied with O'Toole's leadership and his attempts to put a more moderate stamp on the party.

Elect Conservatives, which endorsed Lewis during the 2020 leadership race, issued a statement linking to the petition. The statement said it was "hypocritical" of O'Toole to give Batters the boot, given that the party professes to promote "free speech and open dialogue."

Anti-abortion groups Campaign Life Coalition and RightNow have also endorsed the petition, after weeks of separately saying O'Toole didn't live up to the pledges he made to social conservatives during the leadership race.

This report by The Canadian Press was first published Nov. 17, 2021.