Liberal Leader Justin Trudeau says he's not yet ready to call on the prime minister to step aside as the Senate expenses scandal ensnares more members of the PMO, but for now says the opposition should continue to seek answers and try to restore Canadians' faith in Parliament.

In a wide-ranging interview for CTV's Question Period on Sunday, Trudeau was asked why he has not called for Prime Minister Stephen Harper to resign as the Senate scandal continues to grow.

Trudeau said calling for Harper's resignation "is a very, very serious thing," and said it's "ultimately much more important" to get to the bottom of the issues related to the scandal so Canadians "can make a better appraisal of their leader."

"Opposition leaders who call for the prime minister's resignation anytime something happens in Ottawa begin to lose credibility," Trudeau said.

"And what I'm focused on right now is restoring the credibility of Parliament and of politicians in general for Canadians by emphasizing facts, by getting people to answer honest questions, and to be less focused on cover-up and more focused on governing."

He warned that if, as more information about the scandal is disclosed "it becomes clear that these allegations and these investigations are grounded in the betrayal of trust of Canadians towards their government or seems that it might be, then absolutely there will be a stronger call. But I think we have to be very respectful of our democratic institutions and our Parliament."

Questions about an RCMP affidavit released last week took up much of question period in the House last week, with the opposition demanding answers about some its more explosive allegations.

The document alleges that several PMO staffers, as well as the Conservatives' top bagman, Sen. Irving Gerstein, conspired to whitewash an audit of Sen. Mike Duffy's expenses and ultimately repay Duffy's ineligible claims.

None of the allegations have been tested or proven in court.

The prime minister has long said he knew nothing of the decision by his then-chief of staff Nigel Wright to give Duffy $90,000 to repay his expenses until that deal was reported by CTV News in May.

He also defended his decision to keep Gerstein in the Conservative caucus, saying he is not the subject of the RCMP investigation.

The Liberals are now calling on the RCMP to broaden its investigation to include 12 Conservative staffers named in the affidavit.

Trudeau admits providing ‘fodder' for critics

Meanwhile, a recent Ipsos Reid poll for CTV shows Trudeau's support continues to grow and his party now enjoys a six-point lead over the Conservatives, at 35 per cent support versus 29 per cent for the among decided voters.

The Liberals are also ahead in three battleground provinces: Ontario, Quebec and British Columbia.

The poll results followed a successful byelection night that saw the Liberals handily retain Toronto Centre and Bourassa, and make significant gains in the two Manitoba ridings of Brandon-Souris and Provencher.

Trudeau said he is mindful "to be careful of reading too much into byelections two years away from any general election."

"But certainly we're pleased with the kind of response we're getting right across the country and I think there's reason to be satisfied that the approach that we are taking. Being positive, reaching out around substantive issues and trusting Canadians with the truth and with honesty is giving a certain amount of interest in the Liberal Party that hopefully will translate into votes in 2015."

Trudeau acknowledged that he's "given a certain amount of fodder" to the Conservatives and the NDP with some of his recent political missteps, but says he won't change his approach during the march to the next election.

"Canadians are responding to the person I am, to the values I put forward, and to my openness," he said.

"And yes, there's going to be more learning as there already has been in the coming years, but I'm confident that what people are responding to is someone who is real and connected to them, rather than someone who is overly focused on image and spin and expectations of what a serious leader should look like or sound like."