Kathleen Wynne is warning the opposition to back off in their attacks on her government over an alleged bribery scandal – charging that Progressive Conservative and New Democrat MPPs have secretly tried to negotiate government jobs with the Liberals in exchange for resigning their seats.

With the accusation, the Premier has chosen to fight fire with fire and ramped up an already intense battle over government ethics.

Patricia Sorbara, Ms. Wynne's deputy chief of staff, and Liberal fundraiser Gerry Lougheed are accused of offering a former candidate a government appointment to entice him to quit the Sudbury by-election race. Earlier this week, the province's top elections official ruled the pair broke provincial bribery rules. They are also under criminal investigation by the Ontario Provincial Police.

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Ms. Wynne has steadfastly defended Ms. Sorbara, describing her Friday as "a seasoned professional and a woman of integrity" and saying Ms. Sorbara would only resign if she is charged.

The Premier tried to turn the tables on the Tories and NDP.

"Members of both opposition parties have approached members of my team on a number of occasions suggesting they would vacate their seats if we would guarantee an appointment. We refused each time," she told reporters at a Queen's Park news conference. Then, she demanded the opposition stop accusing Liberals of "being criminals."

Ms. Wynne would not say which PC and NDP MPPs had solicited jobs, only that there were "a number" who approached the Liberals during the previous parliament, which was dissolved in May. In that legislature, the Liberals held only a minority of seats, and resignations of some opposition MPPs could potentially have changed the balance of power.

Former finance minister Greg Sorbara, Ms. Sorbara's cousin, wrote in his recent memoir that he had talks with then NDP MPP Rosario Marchese in 2012 about offering the latter a government appointment in exchange for giving up his seat. The deal never happened, he wrote, because Mr. Marchese wanted a bigger job than Mr. Sorbara was willing to give. Mr. Marchese, Mr. Sorbara said, "mused" about becoming chair of the LCBO, Ontario Power Generation or the Ontario Lottery and Gaming Corp.

"We regularly talked about the possibility of an appointment," Mr. Sorbara wrote. "The problem was that Rosie's aspirations were bigger than what was in my bag of toys." Mr. Sorbara said he instead wanted to give Mr. Marchese a job with the Workplace Safety and Insurance Appeals Tribunal or the Social Assistance Review Board, but Mr. Marchese "argued that those appointments would require too much work and too little profile." Mr. Marchese did not respond to a request for comment Friday.

Also in 2012, the Liberals appointed Tory MPP Elizabeth Witmer chair of the Workplace Safety Insurance Board, prompting her to resign her seat. There was no suggestion she solicited the job.

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The opposition on Friday dismissed Ms. Wynne's comments as a political ploy.

"Today, in a desperate and cynical attempt to distract from the criminal investigations into her staff and Liberal insiders, she threw out slanderous accusations casting a dark shadow over the entire Ontario Legislature," NDP House Leader Gilles Bisson said in a statement. Added Tory House Leader Steve Clark: "If she's going to make those allegations, she needs to give a little more information… She's trying to change the channel."

PC Leader Jim Wilson said Ms. Witmer's appointment to the WSIB was a "patronage" job and that this was "not the same" as the offer to former Liberal candidate Andrew Olivier.

Asked to explain his logic, he said: "If you're looking for logic in this business, you're in the wrong place."