Conservative Leader Andrew Scheer stood outside the House of Commons on Wednesday without the immunity from lawsuits the chamber would afford him and invited Prime Minister Justin Trudeau to sue him for criticism he levelled at the Liberal Leader over his role in the SNC-Lavalin affair.

He also repeated word-for-word the March news release that sparked the threat of legal action.

Mr. Scheer said he welcomes court proceedings over his statements, adding he would like the Prime Minister to be required to testify under oath. Mr. Trudeau, through a lawyer, threatened on March 31 to sue the Conservative Leader for libel for saying he had interfered in the criminal prosecution of SNC-Lavalin Group Inc.

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Later on Wednesday, during Question Period in the House of Commons, Mr. Scheer urged Mr. Trudeau to sue him. “I am not withdrawing my remarks. In fact, I am standing by them ... if the Prime Minister is so sure of his case, will he commence court proceedings so that Canadians can finally hear the truth about this scandal?”

Members of Parliament are protected from legal action for defamation over statements they make in the House, but not outside it.

In Question Period, Mr. Trudeau did not directly address Mr. Scheer’s efforts to provoke the lawsuit. He attacked Mr. Scheer’s credibility, saying the Conservatives "have a history of making false and defamatory statements,” and accusing the Conservative Leader of refusing to disavow white supremacists, misleading Canadians on climate change and failing to produce a workable economic plan.

“The Conservatives actually do not want to talk about anything that actually matters to Canadians in their day-to-day lives,” the Prime Minister said.

“What we have, right here, is a political party that does not want to talk about the economy, that does not want to talk about the budget, that does not want to talk about climate change, that just wants to play politics and attack us."

Mr. Scheer called the white supremacist charge “typical Liberal smear tactics,” saying he has always “denounced white supremacy and racism and anyone who promotes those hateful ideologies.”

Mr. Trudeau did not say whether he planned to follow through on his legal threat. The Prime Minister’s Office declined to comment.

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On March 31, Mr. Trudeau’s lawyer, Julian Porter, wrote a letter to Mr. Scheer that he said should be “treated as notice” of possible action under the Libel and Slander Act of Ontario, citing a March 29 news release that he said went “beyond the pale of fair debate and is libelous.”

On Feb. 27, Jody Wilson-Raybould told the Commons Justice committee that as attorney-general she faced “consistent and sustained” pressure from Mr. Trudeau and top officials, including “veiled threats,” on the need to shelve the criminal prosecution of SNC-Lavalin. Ms. Wilson-Raybould and former Treasury Board president Jane Philpott quit cabinet over the government’s handling of the matter.

Mr. Scheer said on Wednesday he would welcome a battle in court after Liberal-dominated parliamentary committees shut down further hearings into the SNC-Lavalin affair. He said a lawsuit could result in an "an inquiry where Justin Trudeau does not control the proceedings, where he won’t be able to use his majority to shut down an investigation.”

Separately, a former director and chair of the audit committee of the Federal Liberal Agency of Canada, Elbert Paul, told The Globe and Mail he supports Ms. Philpott’s contention that the Liberals broke federal law in the process that led to her expulsion and that of Ms. Wilson-Raybould from the party caucus. On Tuesday, Ms. Philpott asked Commons Speaker Geoff Regan to rule on the matter, including whether it breached the two MPs’ privileges.

“The conduct of Prime Minister Trudeau was a breach of parliamentary rights of the members and was an an ad hoc and arbitrary action,” Mr. Paul said in a statement. “It also deepens Canadians’ profound concern over his failure to establish a public inquiry into the SNC-Lavalin scandal,” he said. He was director of the federal Liberal agency between 1986 and 2016.

At the heart of Ms. Philpott’s argument is that, after the 2015 federal election, the Liberal caucus did not conduct a recorded vote, as required under the Parliament of Canada Act, to decide whether to adopt a set of rules governing the expulsion of caucus members and other matters.

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Liberal MP John McKay has said “there was no vote” when the Liberal caucus met after the 2015 election to decide how to proceed with the rules.

Ms. Philpott says this means the caucus never voted to adopt the rules, including one that said 20 per cent of a caucus must submit written notice to review an MP’s membership, and that MPs can be ejected only if a majority of all caucus members vote to do so in a secret ballot.

Ms. Philpott has also noted no caucus vote took place before Mr. Trudeau expelled her and Ms. Wilson-Raybould last week. Mr. Trudeau has said he consulted caucus before his decision.

The Liberals say they decided as a caucus not to adopt the rules in November, 2015, and communicated that decision to the Commons speaker.