MAPLE, Ont. -- A looming showdown with Ontario teachers, a scandal at the air ambulance service and a hefty bill for cancelling a gas plant isn't deterring Premier Dalton McGuinty from pushing ahead with two byelections that could hand his minority Liberals a majority government.

Voters in Vaughan and Kitchener-Waterloo will go to the polls on Sept. 6, McGuinty said Wednesday after touring a school in Maple, Ont.

The byelections will fill the two seats vacated by Liberal Greg Sorbara and Progressive Conservative Elizabeth Witmer.

Sorbara resigned last week to devote himself to running the Liberals' election campaign, while Witmer was given a plum appointment by McGuinty to head the Workplace Safety and Insurance Board.

Ensuring labour peace in schools will be the key issue in the byelections, McGuinty said after making the announcement in the riding of Vaughan.

He said he's not ruling out recalling the legislature for an emergency session this month to impose a new contract on teachers if they don't reach new local agreements with school boards by the start of the school year.

But McGuinty wouldn't say whether he'd make the legislation a confidence motion, which would force the Tories and NDP to decide whether to plunge the province into another general election.

Governments always have a difficult time winning byelections, but the Liberals are the only party with a realistic plan to secure a public sector wage freeze to eliminate the deficit, he said.

The premier took a shot at his opponents, casting the Conservatives as too far to the right and the NDP too far to the left to preserve gains in education. That could position the Liberals to march straight up the middle on the issue -- a strategy that's worked well for them in the past.

"The PCs, for example, they would put money into horse racing before all full-day kindergarten. I think that's the wrong choice," McGuinty said.

"The NDP are saying they would give teachers pay increases and that money would come out of the classroom. Again, I think that's the wrong choice."

Two hours before McGuinty made the byelection announcement, the government sent out a press release about spending millions of dollars on a new highway between Kitchener-Waterloo and Guelph.

But the premier said he knew nothing about it.

"I'm not familiar with this press release," McGuinty said.

"I do know that Highway 7 is something we've been talking about for a long time in that community, that there has been significant work underway for some time."

Work on the highway was one of the questions he faced during a trip to Kitchener-Waterloo last week. The Liberals maintain the project was included in the spring budget, but said they can't disclose the total cost until all the contracts are signed.

It's no coincidence that the government put out the release on the same day McGuinty announced the byelections, said NDP Leader Andrea Horwath.

The highway is something the people of Kitchener-Waterloo have been waiting five years for, she said. "All of a sudden, it's back on the agenda," she said.

The Liberals have been accused of trying to save seats by pulling the plug on a power plant in Mississauga just days before the last election on Oct. 6, leaving taxpayers on the hook for $190 million.

Finance Minister Dwight Duncan told a legislative committee last month that the Liberal campaign made the decision when they were behind in the polls.

Two years ago, they cancelled plans for another gas-fired generating station in neighbouring Oakville -- also a Liberal riding -- amid vociferous opposition from local residents.

That same year, McGuinty shrugged off accusations of vote-buying in an Ottawa riding after the Liberals provided an estimated $200 million to help Nortel pensioners during a byelection campaign.

They also promised an estimated $15 million to keep a threatened hospital from closing in a downtown Toronto riding on the eve of a byelection. The Liberals ended up hanging onto both seats.

McGuinty will have to face the music over the cancelled gas plant and the fiasco at Ontario's troubled air ambulance service when voters go to the polls this fall, said Horwath.

The controversy over Ornge has heated up in the months since provincial police announced a criminal investigation over financial irregularities. A legislative committee has heard explosive allegations of possible kickbacks, the former CEO's $1.4 million compensation package and the lack of government oversight of the service, which receives $150 million a year.

The voters in Vaughan and Kitchener-Waterloo have an opportunity to send a clear message to the Liberals that they can't be trusted with the power of a majority, Howarth said.

"They have not earned the respect of Ontarians," she said. "They have not earned the confidence of Ontarians. And if fact, since October, we've seen more and more reasons why not to give this government a majority."

None of the three major parties has chosen a candidate for Vaughan. But the two opposition parties have a head start in Kitchener-Waterloo, with Tracey Weiler running as the Tory candidate and Catherine Fife for the NDP. Stacey Danckert is the Green Party candidate.

Horwath said Fife, a former local school board trustee and president of the Ontario Public School Board Association, will be an asset in talking about education issues during the campaign.

With the departure of Witmer and Sorbara, the Liberals have 52 seats while the PCs and NDP have a total of 53 seats.