Prime Minister Stephen Harper is losing an ardent champion of his government's tough-on-crime agenda with Vic Toews' departure from federal politics the latest signal of a looming cabinet overhaul.

Mr. Toews resigned on Monday to "pursue opportunities in the private sector." His resignation as a cabinet minister, MP and regional minister for Manitoba takes effect on Tuesday.

The departure of the Public Safety Minister, who stick-handled the passage of a bill to kill the long-gun registry but also the failure of legislation to increase Internet surveillance, further reduces the cabinet presence of MPs predating Mr. Harper's united Conservative Party.

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Mr. Harper was expected to announce a cabinet shuffle as early as Wednesday, one that appears likely to offer fresh faces to the front bench, although an MP said the train derailment and fire in Lac-Mégantic, Que., meant "all bets are off" on the timing.

Some other veterans will be left out. Fisheries Minister Keith Ashfield, who has cancer, asked to be excluded from cabinet, while Environment Minister Peter Kent has suggested he may be out also. Ted Menzies, Minister of State for Finance, has said he will not seek re-election and therefore wants to leave cabinet. Diane Ablonczy also will not run again, but stayed quiet on whether she expects to stay on as a minister.

Details of the shuffle are closely guarded, and some ministers' staff professed on Monday to have been told nothing. But sources said those included in cabinet – and some on the outs – already know their fate.

Mr. Toews, 60, has been signalling for some time he will step down. In a statement, he thanked his constituents, volunteers and staff while praising Mr. Harper as "a man of great character and integrity."

First elected as a Canadian Alliance MP in 2000, Mr. Toews said he worked to unite Canada's conservative movement. "Looking back, I believe I accomplished what I did because of my desire to work with other like-minded people," he said. The Manitoba MP served as minister of justice and president of the treasury board before becoming Public Safety Minister in 2010.

Mr. Toews is best known as a hard-liner on crime. As justice minister, he imposed mandatory minimum sentences and reduced the use of house arrest. He also killed the long-gun registry, raised the age of consent and boosted efforts to deport criminals who are in Canada illegally.

But his attempt to give police power to monitor Internet users sparked a storm of protest. It also prompted a Liberal staff member to post salacious details online about Mr. Toews' messy divorce from his wife of 30 years.

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Mr. Toews has remarried and, in his resignation statement, said: "I would like to thank my spouse, Stacey, my children and my extended family and friends for their patience and understanding."

Before entering federal politics, Mr. Toews was a lawyer and a provincial MLA. In one provincial campaign, he exceeded spending limits by $7,500 and was fined $500.

Manitoba Progressive Conservative leader Brian Pallister, elected federally with Mr. Toews in 2000, said the departing MP helped spur "a resurgence of Conservatism" in Canada. "Vic certainly demonstrated a lot of wonderful qualities over a long period of time in public service. And I think it's important to respect those. We need more of those kinds of people," Mr. Pallister said.

NDP MP Randall Garrison, the critic for Mr. Toews' portfolio, said he hopes for a "less ideological" successor. "Like most Canadians, I do welcome his move to the private sector," Mr. Garrison said.

Mr. Toews "brought a wealth of experience" to cabinet because of his time in provincial politics, said Stockwell Day, a former federal Conservative cabinet minister. Mr. Day said he expects surprises and disappointments in the new shuffle, but added that Mr. Harper looks for people who can balance the work as an MP. "He has to be confident that you can handle your constituency load as well as your portfolio."