Leader of the Opposition Andrew Scheer rises during Question Period in the House of Commons Wednesday, March 20, 2019 in Ottawa.

Members of Parliament are continuing their marathon voting session Thursday as opposition parties protest the Trudeau government’s efforts to shut down any further investigation into the SNC-Lavalin affair.

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The Liberal majority shot down a Conservative motion calling on Prime Minister Justin Trudeau to let former attorney general Jody Wilson-Raybould testify more fully about her allegation that she was improperly pressured to drop a criminal prosecution of Montreal engineering giant SNC-Lavalin.

WATCH: Justin Trudeau reiterates claim SNC-Lavalin jobs were ‘at risk’

The motion was defeated by a vote of 161-134.

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That set the stage for a Conservative-sponsored filibuster Wednesday night, requiring 257 separate votes on items in the government’s spending estimates.

LISTEN MORE: Jane Philpott says there is “much more” to the SNC-Lavalin affair than has been made public

Since any vote involving government spending is automatically considered a confidence vote, Liberals were required to be out in force to avoid potential defeat of the government.

The voting could theoretically last 36 hours, but the Conservatives have only to keep it going until just after 10 a.m. today to scrub the remainder of the parliamentary day.

Wilson-Raybould has already testified for nearly four hours before the committee, having been granted a waiver from solicitor-client privilege and cabinet confidentiality to freely discuss events from last fall – when the inappropriate pressure was allegedly applied – until Jan. 14, when she was shuffled out of the dual justice and attorney general post to Veterans Affairs.

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The Conservative motion called on Trudeau to extend the waiver of cabinet confidentiality to cover the period from Jan. 14 to mid-February, when Wilson-Raybould resigned from cabinet.

READ MORE: Opposition MPs briefly storm out of committee meeting as Liberals end SNC-Lavalin investigation

Wilson-Raybould has said she has more to say about what occurred after she was shuffled, but she was not in the Commons for the vote on the Conservative motion. Nor was Jane Philpott, who resigned from cabinet in solidarity with Wilson-Raybould early this month, saying she’d lost confidence in the government’s handling of the SNC-Lavalin file.

WATCH: March 10 — Scheer says Trudeau must let Jody Wilson-Raybould speak at committee in full

However, the Conservatives are not giving up just yet. They are asking the Commons ethics committee to launch its own investigation into the affair, starting with calling Wilson-Raybould to testify by no later than March 27. The Liberal-dominated committee is to consider the request on Thursday.

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A month ago, when the Commons voted on another opposition motion to let the former minister testify freely, Wilson-Raybould abstained but then added fuel to the SNC-Lavalin fire by saying: “I understand fully that Canadians want to know the truth and want transparency; privilege and confidentiality are not mine to waive and I hope that I have the opportunity to speak my truth.”

WATCH: The Conservatives drowned out Finance Minister Bill Morneau’s delivery of the budget speech on Tuesday by loudly chanting “let her speak”

Liberals nervously waited to see whether she or Philpott would bring another can of gas to Wednesday’s vote. They did not, adding to Liberals’ professed comfort at letting the pair remain in the governing caucus and seek re-election as Liberals this fall, despite their lack of confidence in the prime minister.

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READ MORE: Trudeau names former Liberal justice minister as special adviser amid SNC-Lavalin affair

Wilson-Raybould attended part of a closed-door Liberal caucus meeting Wednesday morning but Philpott did not show up.

“They’ve both indicated that they continue to believe in the Liberal party and want to stand for us in the election in the fall. I look forward to continuing to work together,” Trudeau said on his way into the caucus meeting.

“You know, sometimes there are differences of opinion but we’re a big tent,” echoed Liberal caucus chair Francis Scarpaleggia, a Quebec MP.

Despite the efforts to unite and put the affair behind them, one source said Philpott faced a “frank and emotional” session with her Ontario caucus colleagues prior to the national caucus meeting she did not attend. And both Philpott and Wilson-Raybould were allowed to miss the marathon voting session, in the belief that sleep-deprived Liberal MPs might take out their frustration on the pair as the voting dragged on into the wee hours of the morning.

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The source spoke on condition of anonymity because he was not authorized to publicly discuss confidential caucus matters.

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