QUEBEC - The most controversial minister in Quebec's scandal-plagued government has been booted from cabinet, expelled from the Liberal caucus, and the provincial police have been called in to investigate him.

Premier Jean Charest made the announcement Thursday at a hastily called news conference.

He said he turfed Tony Tomassi after learning that he had used, while he was a member of the legislature but not yet a cabinet minister, a credit card belonging to a private security firm.

That security firm is now at the centre of one of several allegations of illegal fundraising dogging the Charest government.

"Mr. Tomassi confirmed that he used for a certain period of time this card belonging to (the company) BCIA," Charest told reporters.

"These are troubling facts that raise questions. As premier of Quebec and head of the government, I cannot accept a situation like that."

With four of his ministers being probed for fundraising irregularities, questions about his own $75,000-a-year bonus funded by the Liberal party, widespread calls for a public inquiry into corruption, and his ex-justice minister declaring that party bagmen called the shots when it came to naming judges, Charest's problems were clearly not limited to Tomassi.

But the embattled minister had, lately, become a major source of them.

Tomassi was pounded by controversy for months, starting with suggestions that permits for public daycare spaces were going to his personal friends and Liberal party donors.

He had, on Thursday, become the fourth minister in the Charest government to fall under the microscope of the province's chief electoral officer.

The probe was prompted by a newspaper report that suggested illegal contributions had been funneled into Tomassi's riding association, breaking not only the ban on corporate donations but also the $3,000 personal contribution limit. A number of BCIA employees told La Presse newspaper they were each given free tickets to a $500-a-plate fundraiser.

Tomassi will be replaced as family minister by Immigration Minister Yolande James.

The opposition says Charest's move doesn't go far enough; they want a public inquiry that would examine the fundraising of a governing Liberal party they call corrupt.

They also want more details on the $75,000 separate salary that the Liberal party has paid Charest for years, including information about how that money is raised.

The Opposition says the premier should earn his living from the government alone -- and not from party donors.

One reporter, during a news conference Thursday, asked what the difference was between Tomassi using a corporate credit card and Charest collecting a separate salary that the Liberal party raises from donors.

The spate of scandals has sent Charest's popularity spiralling downward in recent months.

He was elected to a third term in 2008, with a majority government, and he enjoyed rock-solid poll numbers throughout the recession.

Then the scandals started, and he saw the same kind of collapse in public support that the federal Liberals witnessed in the wake of the sponsorship scandal.

Until he dispatched Tomassi to a Helena Guergis-like fate on Thursday, Charest had staunchly defended his minister.

Guergis was a federal minister cabinet minister, until the prime minister recently booted her from caucus and suggested the RCMP explore some undisclosed behaviour which he did not publicly discuss.