OTTAWA -- Liberals are defending Justin Trudeau's threatened libel suit against Andrew Scheer, arguing that the Conservative leader's editing or deleting online statements proves he knows he's gone too far in criticizing the prime minister's handling of the SNC-Lavalin affair.

"The leader of the Opposition pretends that he will not back down and he tries to make a show out of it," Government House leader Bardish Chagger told the House of Commons on Monday. "We know that is false because while he is saying that, he has already been editing online statements or erasing them entirely."

Scheer revealed Sunday that he'd received a letter from Trudeau's lawyer, Julian Porter, serving notice of a possible libel suit over a statement issued on March 29, in which the Conservative leader accused Trudeau of leading a campaign to politically interfere with the criminal prosecution of Montreal engineering giant SNC-Lavalin and directing his former attorney general, Jody Wilson-Raybould, to break the law.

The notice is not an actual lawsuit, just a threat that one might come -- a standard first step in a defamation claim. In the Commons on Monday, Scheer repeatedly taunted the Liberals to bring it on.

"Canadians are looking forward to the prime minister finally appearing under oath and testifying in a setting that he, himself, cannot control," Scheer said, repeatedly asking the government to set a date for legal proceedings to begin.

Scheer denied having edited or deleted any posts on Twitter.

"No, I have not deleted tweets because I stand by everything I said in those statements," he said.

But Chagger pointed to a tweet Scheer posted on March 31, the same day he received Porter's letter. Originally, it referred to Trudeau telling "lies" about not knowing about a conversation the clerk of the Privy Council, Michael Wernick, had with Wilson-Raybould on Dec. 19. The tweet was later deleted and a new one posted, she said, to replace the word "lies" with "falsehoods."

Wilson-Raybould surreptitiously recorded that conversation with Wernick to bolster her contention that the top public servant had issued "veiled threats" that her job as justice minister and attorney general was at risk if she didn't agree to intervene to stop the prosecution of SNC-Lavalin on bribery charges related to contracts in Libya. Wernick's lawyer said the clerk never relayed that conversation to Trudeau because everyone went on holiday the next day. When they returned in the new year, the lawyer said, they got consumed with planning a cabinet shuffle, in which Wilson-Raybould was moved to Veterans Affairs.

Chagger pointed to another tweet Scheer posted on Feb. 11, in which he asserted there is "potentially criminality at play in the Prime Minister's Office." That tweet was deleted, she said.

And she brought up a tweet Scheer deleted back in December after Innovation Minister Navdeep Bains served notice of a potential libel suit over the Conservative leader's assertion that the minister was under RCMP investigation related to a land deal in Brampton.

"It is important that Canadians always know that we will not stand idly by while the Conservatives intentionally mislead Canadians," Chagger said, adding that the Conservatives and their leader "have a history of making untrue and defamatory statements just for political gains."

Scheer spokesman Brock Harrison said tweets such as the ones Chagger referred to "are deleted and reposted for a number of reasons, usually to correct typos or to better align the language between English and French."

"However, contrary to what Ms. Chagger implied in question period, Mr. Trudeau's threatened lawsuit has nothing to do with these tweets or any other tweets," Harrison said.

In 2008, then Conservative prime minister Stephen Harper launched a libel suit against the Liberal party over allegations that he had known about an alleged attempt by Conservatives to bribe independent MP Chuck Cadman in exchange for his support in a key confidence vote in 2005.

The lawsuit made it difficult for then Liberal leader Stephane Dion to raise the issue during the 2008 election campaign. A few months after the election, which returned Harper's Conservatives to power with a minority in Parliament, Harper settled the matter out of court with Dion's successor, Michael Ignatieff.