Why won't Trudeau release classified names — and why won't Poilievre get a security clearance?

Prime Minister Justin Trudeau made waves Wednesday by turning what started as an examination of his government's response to foreign interference into a pointed criticism of Conservative Leader Pierre Poilievre.

"I'm getting a little more partisan than I tried to in this case, but it is so egregious to me that the leader of the Official Opposition, who is certainly trying very hard to become prime minister, is choosing to play partisan games with foreign interference," Trudeau told the public inquiry into foreign interference on Wednesday.

Trudeau went after Poilievre over the Conservative leader's refusal to receive a security clearance and get briefed on top-secret and classified information regarding his party and some of its members.

Poilievre responded with a lengthy statement that included a claim that Trudeau was lying under oath and called on the prime minister to release the names of allegedly compromised politicians.

In testimony before the inquiry, the prime minister said he had seen the names of Conservative parliamentarians who are "engaged, or at high risk of, or for whom there is clear intelligence around foreign interference." He said that while he directed CSIS to pass that information along to Poilievre, the agency is unable to do so without giving him a security clearance first.

"The decision of the leader of the Conservative Party to not receive the necessary clearance to get those names and protect the integrity of his party is bewildering to me and entirely lacks common sense," Trudeau added.

Trudeau later said under cross-examination that he was aware of members of other parties, including his own, being vulnerable to foreign interference activities.

Wesley Wark, a national security expert with the Centre for International Governance Innovation, said Trudeau's testimony wasn't terribly revealing.

"Prime Minister Trudeau made this sound a bit more sensational I think than it was," Wark told CBC News.

Wark pointed to the report the National Security and Intelligence Committee of Parliamentarians (NSICOP) released in June, which suggested some parliamentarians had been "'semi-witting or witting participants" in foreign interference activities.

CSIS officials testifying before the inquiry called into question some of the conclusions in the NSICOP report. One CSIS official, in an interview behind closed doors, specifically questioned the use of the word "witting."

Wark also said it's not clear to what extent the unnamed parliamentarians could be compromised — and suggested many may not even be aware that they are.

"We're talking about people who are being lured into the embrace of foreign threat actors in ways that they may not even fully appreciate themselves," he said, noting that most foreign actors are looking to "groom" politicians.

Richard Fadden and Ward Elcock — two former CSIS directors — told CBC News' Power & Politics on Wednesday that Trudeau probably shouldn't have taken such a partisan turn in his testimony.