TORONTO - Former labour minister Peter Fonseca should resign his seat in the Ontario legislature now that he's been appointed as a Liberal candidate in the next federal election, the opposition parties said Wednesday.

Federal Liberal Leader Michael Ignatieff on Monday appointed Fonseca as a candidate in the Mississauga East-Cooksville riding that he still represents provincially, eliminating the need for Fonseca to win a local nomination meeting.

The Progressive Conservatives and New Democrats said Fonseca should quit the legislature now, instead of waiting until Prime Minister Stephen Harper calls an election, so he can focus his attention on becoming a Member of Parliament.

"Do the honourable thing, step aside, and demonstrate to his constituents, and to society at large, that he has some integrity and that he's going to be honest about this," said Opposition critic Randy Hillier. "He wants to have his cake and eat it as well."

NDP critic Peter Kormos said Fonseca has "no business running as a federal MP while he's collecting an MPP's salary."

"He's got to resign."

Fonseca, who was not immediately available for comment Wednesday, was dropped from cabinet last week after he told reporters -- but not Premier Dalton McGuinty -- that he was considering a run for federal office.

The optics were terrible for the Liberal government as Fonseca made the comments about his career during the release of a report into the deaths of four Toronto construction workers last Christmas Eve.

Fonseca complained this week about journalists raising questions about his bid for federal office during the release of the workplace safety report, but "Fonseca made his own bed," said Hillier.

"If he wanted to keep that close to his chest it would have been kept close to his chest, that announcement (about running federally)," said Hillier.

"As minister, he was willing to disregard his ministerial duties in favour of his political aspirations by having that story come out at the same time (as the report into the workers' deaths)."

The New Democrats also complained about what turned out to be Fonseca's last actions as Ontario's labour minister.

"What we saw last week was a purported minister of labour who had little interest in labour and the health and safety of working people and far more interest in his own future," said Kormos.

McGuinty would not have to call a byelection to replace Fonseca because it is less than a year until the next Ontario election Oct. 6.

The premier's office said Wednesday that the opposition parties really don't have a leg to stand on when it comes to trying to force Fonseca to quit just because he's now a federal candidate.

The Liberals pointed out Jim Flaherty and John Baird both sat as members of the Ontario legislature after they had become federal Conservative candidates, and that at least two New Democrats had done virtually the same thing.

McGuinty's office said Fonseca was expected to stay as a member of the Ontario legislature until the federal election is called, which is widely expected to happen next spring.