Prime Minister Justin Trudeau has named Steven MacKinnon as Canada's new minister of labour and seniors, filling a fresh vacancy on his front bench, left by outgoing minister Seamus O'Regan.

MacKinnon arrived at Rideau Hall on Friday morning, and was sworn in to his new role, shifting from his current spot as government House leader.

The Gatineau, Que., MP had been filling in for Karina Gould in that post, while she was on parental leave. Gould is expected to return in July, ahead of resuming stewardship of the government's legislative agenda come the fall sitting of Parliament.

"Lovely day," MacKinnon said, on his way in to the snap ceremony. As the minister responsible for federally regulated workplaces, and the facilitator in collective bargaining, he'll quickly have to get up to speed ahead of a potential national rail strike.

"I believe that my job will be to ensure that the economy continues to allow for competitive businesses and allow for healthy workplaces, where workers are well compensated," he said, in a brief press conference following his swearing-in.

In a statement about the change to the ministry, Trudeau's office noted that MacKinnon has "accumulated a wealth of experience building consensus and working with partners."

Facing reporters' questions about the state of the Liberals, MacKinnon stood by Trudeau and the direction his slumping minority government is going.

"I detect a resolve among all of my caucus and cabinet colleagues to continue doing the work as we enter what will undoubtedly be a productive year… a challenging year," he said. "We all have confidence that the prime minister will guide us through that."

"If we've learned nothing over the past few weeks, is what we assume to be true today in politics is not necessarily going to be true tomorrow," said MacKinnon.

Rare summer cabinet meeting

Friday's minor change to cabinet comes amid speculation over a looming larger summer shuffle and chatter about efforts to recruit former Bank of Canada governor Mark Carney, potentially to replace Chrystia Freeland as finance minister. This is all linked to pressure the prime minister is facing to mount a successful political refresh.

It also comes just ahead of Trudeau holding a brief virtual meeting with his cabinet on Friday, the first meeting of its kind, since last month's major Toronto byelection defeat. The Prime Minister's Office has said the short conversation was called simply to discuss outstanding "appointments," ahead of Trudeau taking some time off.

"It was a very straightforward meeting, we had some appointments to do, and that was that," Families Minister Jenna Sudds said in an interview on CP24.

O'Regan announced Thursday that he was stepping down from cabinet as of Friday, citing a desire to spend more time with family.

The prominent Atlantic MP and longtime friend of Trudeau intends to keep his seat until the next election, but won't be running again, making him one of more than a dozen Liberal MPs who have already indicated they don't plan to re-offer come the next federal election.

His surprise announcement sparked more chatter about the potential for others to consider following suit, considering the fight ahead.

Pollster Nik Nanos said that as it stands, Trudeau's "political coattails are pretty short," which means Liberal MPs are having to prepare to run on their own records and reputations.

"I think you're going to see a lot of hand-wringing among MPs as they take a lot of grief in their ridings. And the prime minister himself, personally, is going to have to decide what is his future? Is he going to stay in office? If he is, will he make changes?" political analyst and Liberal Scott Reid said on CTV News Channel Friday.

"The government has to still come to grips with, in light of this year of bad polls… what are they willing to do to genuinely change course?" Reid said. "A lot of Liberals will tell you, at least privately, that staying the course means to sink for certain."

With files from CTV News' Jeremie Charron