Prime Minister Stephen Harper will shuffle his cabinet Tuesday, but most of the top ministers are expected to keep their portfolios.

Over the weekend, Veterans Affairs Minister Greg Thompson resigned from cabinet, saying he won't be running in the next election, leaving at least one post to be filled.

CTV Ottawa Bureau Chief Robert Fife said there is speculation that Treasury Board President Vic Toews could step down and some junior ministers could be moved around.

Fife told CTV News Channel it is highly unlikely that any of the top-ranking ministers involved with the Haiti relief efforts, such as Defence Minister Peter MacKay, Immigration Minister Jason Kenney or Foreign Affairs Minister Lawrence Cannon, would be moved.

"They have a lot on their plate right now and the last thing the prime minister would want to do would be to move people involved in pretty serious work at this point," he said.

Late Monday, cabinet ministers were tight-lipped about the impending shuffle.

"I won't even begin to speculate," MacKay told CTV's Power Play.

There has also been some speculation that former foreign affairs minister, Maxime Bernier, could make his way back into cabinet in the shuffle.

The cabinet shuffle will be announced on the same day as the Liberals start their two-day winter caucus meeting.

Late Monday, The Canadian Press reported that Natural Resources Minister Lisa Raitt is expected to lose her post. Last year, a tape recording captured her criticizing other Tory ministers.

Raitt may get shuffled to the Labour portfolio, while Public Works Minister Christian Paradis could take over as natural resources minister.

In another surprise move, The Canadian Press reports that Rona Ambrose -- currently the labour minister -- may get the high-profile position of Public Works.

Ambrose was formerly the Conservatives' environment minister, but lost that post in January 2007 as the Tories faced criticism for moving away from Canada's Kyoto targets on greenhouse gas emissions.