The Parti Quebecois government has delivered a warning for the province's corruption inquiry to watch where it treads, as its testimony spirals off onto a damning and unpredictable path.

Both Premier Pauline Marois and her deputy premier issued similar messages while leaving a caucus meeting Thursday: Marois said the judicial inquiry should show some "prudence," and her deputy premier Francois Gendron urged it to "be more careful."

The message was delivered after sensational testimony this week veered off into unexpected areas, and it wasn't just tarnishing the old Charest Liberals.

This latest testimony has damaged a number of reputations -- including that of a Parti Quebecois stalwart and, most recently, a sitting judge.

The reaction in Quebec City is a far cry from that of the last few years, when scandals overwhelmingly tarred the Liberals and the PQ, then in opposition, would seize upon each allegation until a public inquiry was finally called.

Just recently, the PQ extended the inquiry's deadline after having made anti-corruption measures the centrepiece of its first legislation in office.

Its sudden expressions of wariness come while the inquiry shifts its focus to provincial politics, away from the municipal scene -- and it hasn't been pretty so far.

A major witness this week explained how he gained influence in politics, and ultimately won public construction contracts, by offering things like illegal political donations and get-togethers with celebrities such as hockey stars.

His testimony implicated politicians of different party stripes, and different levels of government.

In his latest claim, he even said Quebec Superior Court Justice Michel Deziel once helped orchestrate an illegal political financing scheme at the municipal level.

Gilles Cloutier said Deziel was still a lawyer at the time, and was organizing the election campaign for the incumbent mayor of Blainville in 1997. Cloutier said Deziel summoned him to his office, handed over $30,000 and told him to find strawmen to pose as donors contributing $750 each.

Cloutier said Deziel knew that he could easily find people as they'd worked together previously. At one point today, Cloutier said he was "good" at working out collusion schemes -- although, he soon added, he wasn't proud of it.

Cloutier, who worked for Roche Engineering Inc. at the time, said he was told the money -- $100 bills in a white envelope -- came from rival firm Dessau Inc.

"He (Deziel), being a lawyer, going to launder $750 donations, would reflect poorly on his code of ethics," Cloutier said Thursday.

"A lawyer, going door-to-door for cheques for a political party . . . that's why he asked me."

He said he did as he was told and found people to write legal-looking cheques in about a week.

Cloutier said he asked friends and acquaintances to help by writing cheques for then-mayor Pierre Gingras' Action Civique Blainville -- offering $300 tax credits to those agreeing to write cheques. Cloutier said the two conversations he had with Deziel occurred without witnesses.

Cloutier said Roche was hard-pressed to get any work in Blainville, a suburb north of Montreal. He says the mayor was constantly on fishing trips with Dessau executive Rosaire Sauriol, and that company got the contracts.

So Cloutier said he started investing in the opposition party. And when it took power, the contracts started coming to Roche.

Deziel, a Blainville lawyer, was appointed to Quebec Superior Court in November 2003. His colleague, Justice France Charbonneau, is presiding over the corruption inquiry. The Canadian Judicial Council announced Thursday that it would investigate the claims against Deziel.

After sharing the anecdote, it was Cloutier who pointed out that his former ally had been named to the bench in 2003.

"It was fraud. I had to mention it," the witness said.

His testimony has clearly irked the governing party.

Gendron, in particular, expressed frustration that the inquiry had broadcast a video of a party hosted by Cloutier in which politicians of different stripes, including the PQ, were seen mingling with construction-industry figures, sports celebrities, and even a Roman Catholic cardinal.

He said he feared that the video, aired without sufficient context, would leave people with the unfair impression that all politicians were guilty of wrongdoing.

At one point Thursday, an anonymous source was even quoted in a news report complaining that the inquiry had allowed the integrity of a PQ ex-minister be called into question without letting his side of the story be reflected at the same time.

Later in the day, the provincial justice minister emerged to stress that the government supported Charbonneau's independence.

"She's in charge of the witnesses that she calls; she's in charge of how she proceeds; and I, as justice minister, will not comment on the testimony or how the Charbonneau commission is unfolding," Bertrand St-Arnaud said.

The opposition wasn't satisifed.

One opposition party, the Coalition, accused the government of attempting to intimidate the inquiry. Jacques Duchesneau, a former anti-corruption czar turned politician, called it "political bullying."

His party leader, Francois Legault, described Marois' comments as "a serious offense."

A day earlier, Cloutier had made a particularly damning allegation about a prominent Pequiste: he said he paid $100,000 to a friend of a PQ transport minister in order to have access to him.

He said that after he paid the sum, he got help from that minister, the now-retired Guy Chevrette, in overturning a municipal construction contract to a rival company and then winning the contract on a subsequent try.

Chevrette has vigorously denied the allegation, calling it defamatory. A lawyer representing him sat next to the Parti Quebecois' own lawyer on Thursday and made a request to question the witness when the inquiry resumes.

But the former senior PQ minister's name surfaced again during the hearings Thursday. Cloutier recalled agreeing to organize an event for a PQ candidate in Prevost, Lucie Papineau, in the fall of 2001.

Cloutier said that even though he was a "good Liberal," he agreed to do it but absolutely insisted that Chevrette attend the fundraiser. He wanted Chevrette there because, he said, he knew and liked him and knew he'd be a big draw as transport minister.

Cloutier said 15 construction executives paid $1,000 a head for access -- specifically, for five minutes of Chevrette's time to air grievances.

Cloutier explained that engineering firms donated to provincial parties, with the money often raised through inflated expense claims on public-works contracts.

He said that provincial donations were, to some extent, made in the hope of winning contracts. But he said they were done mainly to cultivate key contacts in different ministries to help lobby for provincial subsidies to kick-start municipal projects.

"There's no contracts without the subsidies," he said.

He estimated that "business development" techniques accounted for as much as 30 per cent of Roche's business.

He was subjected to a grilling under cross-examination later Thursday.

A Parti Quebecois lawyer asked him whether he believed his illegal spending during the 1995 independence referendum was responsible for swinging the election result. Canada stayed together after a vote decided by less than one percentage point.

Cloutier didn't bite. He said he didn't believe the spending had made a difference. The longtime Liberal said he'd used off-the-books money to pay for billboards and security.

A lawyer representing Roche painted Cloutier as a rogue employee who had issues with authority. Lawyer Michel Massicotte suggested that Cloutier left Roche after stricter rules were implemented under new management.

Cloutier disagreed, saying he'd had a falling-out with a senior executive, France Michaud. Cloutier left Roche and eventually joined rival Dessau in 2006.

The inquiry began a one-week break after Thursday's testimony. It will continue with the cross-examination of Cloutier on May 13.