OTTAWA -- Conservative Leader Andrew Scheer sees the Senate as “an option” for a secondary parliamentary investigation into allegations of PMO interference in the SNC-Lavalin case, should the House justice committee’s limited probe fall flat.

On CTV’s Question Period, Scheer was asked if he plans to approach Conservative senators about seeking a study of the issue, if the House committee does not agree to hear from Jody Wilson-Raybould or other senior PMO officials on the matter.

“That is certainly another option, you know. The prime minister likes to pretend that the people that he's appointed to the Senate are independent… so this will be an opportunity to put that to the test,” Scheer told host Evan Solomon.

After a tense public meeting last week, the House Justice Committee will be meeting in-camera on Tuesday afternoon to discuss other possible witnesses, the timeline for the meetings, and the potential impact on ongoing court proceedings of this probe.

At that meeting, the House committee agreed to a study but used their majority standing to shut down opposition calls for Wilson-Raybould and other key figures in the Prime Minister’s Office to testify. Instead the only witnesses they’ve agreed to hear from are current Justice Minister David Lametti, his deputy minister at Justice Canada, and Clerk of the Privy Council Michael Wernick.

This all comes after The Globe and Mail has reported that the Prime Minister's Office pressured Wilson-Raybould -- who was the attorney general at the time -- to have federal prosecutors pursue a remediation agreement rather than criminal prosecution in the corruption and fraud case against SNC-Lavalin. CTV News has not independently verified the story.

Scheer said that at Tuesday’s meeting the Conservative members on the committee will once again try to get approval for their full desired witness list that includes several others who are believed to be at the centre of this affair. This includes Principal Secretary to the Prime Minister Gerald Butts, Senior Advisor to the Prime Minister Mathieu Bouchard, and former ministerial Chief of Staff to Wilson-Raybould, Jessica Prince.

The motion that the committee passed dictates that members will more broadly study the topics at the heart of the affair: remediation agreements, the Shawcross doctrine -- which has to do with the independence of the attorney general in making decisions -- and the discussions between the attorney general and government colleagues on SNC-Lavalin.

“I think Canadians are sick and tired of hearing what Justin Trudeau is willing to tell us about what his conversations were with the former attorney general, it's time that we hear from her directly,” Scheer said. He described Tuesday’s meeting as “one last opportunity” for the committee to agree to dig deeper.

And if they don’t? “It's a complete sham at that point,” Scheer said.

“If they again prevent the people who are actually involved in the scandal from telling what happened or explaining their side of the story, then it's a complete cover up and it is just an attempt to distract and to deflect. At that point we'll be exploring other tools that we may have to get the light shone on this.”

Liberal members on the committee have said they are still open to adding more witnesses but when asked if that includes Wilson-Raybould they could not commit.

In a separate interview on CTV’s Question Period, Public Services and Procurement Minister Carla Qualtrough wouldn’t weigh in on whether or not she thinks that Wilson-Raybould should testify.

“The Justice committee is an independent committee and they will make their decisions and they will call their witnesses, and this will proceed as it does in committee independently,” Qualtrough said. “We have to let them do the business of their committee and see where it leads.”

There have been murmurings of senators proposing an upper chamber investigation of their own. For some Senators it won’t be the first time they’ve discussed remediation agreements and desired testimony from Wilson-Raybould.

Back in May of 2018 the Senate Legal and Constitutional Affairs Committee looked into the concept of remediation agreements, otherwise known as deferred prosecution agreements. The change to the Criminal Code is the mechanism that SNC-Lavalin then went on to lobby parliamentarians on, arguing in favour of a deferred prosecution agreement as their desired way to settle the fraud case.

At the time, senators requested to have Wilson-Raybould testify to the change but she was not available. Instead she sent her parliamentary secretary Marco Mendicino. Qualtrough testified as well. While not her file, Qualtrough is a lawyer.

In their findings following the study, senators expressed frustration that Wilson-Raybould did not make herself available on this topic, and were critical of the way the change was being introduced as part of an omnibus budget bill.

“[In] the Senate the dynamic is different, so there will be an opportunity if the Senate does proceed that way to prove that they are able to operate in a more independent nature. We’re going to keep pushing on this,” Scheer said.

During the interview Scheer was asked what his position was on deferred prosecution agreements and he did not directly answer, saying that whatever tool Parliament grants to the justice system, it’s incumbent that they be allowed to use them independent of any political considerations.