TORONTO -- Ontario's opposition leaders said Tuesday there was no reason for the legislature to sit dark for months while the Liberals pick a new leader to replace Dalton McGuinty.

McGuinty surprised everyone Monday night by announcing his resignation and proroguing the legislature when the minority government was under fire for cancelled power stations and problems at the Ornge air ambulance service.

"I respect his decision to resign, but I don't respect and I sharply disagree with shutting down business in the house," Progressive Conservative Leader Tim Hudak told reporters.

"Dalton McGuinty walking off into the sunset was no surprise. What does surprise me is that he's decided to cancel the legislature. He decided to lock the place up."

The Liberals need the legislative break not to pick a new leader, but to avoid "facing the music" over their decision to cancel two power plants to save Liberal seats, at a cost to taxpayers of at least $230 million, said NDP Leader Andrea Horwath.

"Once again this is about the Liberals and what they think is best for them instead of what's best for the people of Ontario," said Horwath.

"Everybody realizes that minority parliament isn't easy, and certainly the McGuinty Liberals had a hard time trying to figure out how to deal with it, but the answer isn't to simply throw up your hands and walk away."

Political science professor Henry Jacek at McMaster University in Hamilton said McGuinty may have wanted to avoid the controversies. But he accepts McGuinty's explanation that he prorogued the legislature because the minority government couldn't get support for its plan to freeze public sector wages for two years to trim the $14.4-billion deficit.

"There's no doubt the Ornge hearings and the contempt motion he found to be really annoying," said Jacek.

"I think what had happened was by the beginning of October he realized that he was not going to be able to get his pay restraint package through the legislature, that the Conservatives would not support it, and he was really at a dead end because he couldn't basically control the public finances of the province."

Liberal president Yasir Naqvi didn't want to speculate on how long it would take the party to organize a leadership convention, but Jacek predicted it would be in late January or early February, and would be followed shortly by a throne speech, a provincial budget and an election call.

"As soon as the budget is delivered, the new leader will prorogue the house and call an election," said Jacek.

McGuinty told his ministers Tuesday they would have to quit cabinet if they were to run for his job. Most said it was premature to talk about such announcements.

Environment Minister Jim Bradley, a 35-year veteran of the legislature, was the only minister to flatly rule out a run at the leadership, while Finance Minister Dwight Duncan, who used to say he was too "charismatically challenged" to be leader, was the only one to admit he is considering the idea.

McGuinty said Monday he will stay on until the Liberals elect a new leader, adding the timing of the recall of the legislature would have to wait until then.

"I want my successor to make that decision," he said.

The Ontario Federation of Labour said proroguation just might give the government time to work out a deal with the public sector unions.

"There's no question about it, labour is interested in negotiations with the government...and I do expect to get an agreement on the wage freeze," said OFL president Sid Ryan.

However, the Canadian Union of Public Employees called McGuinty's move to prorogue the legislature an affront to democracy.

"The premier is trying to duck a scandal of his own making," said CUPE Ontario president Fred Hahn.

"He and his colleagues should have the strength of character to stand in the legislature and face the music over their costly attempt to buy votes by cancelling electricity plant contracts."

Credit rating agency Standard and Poor's issued a statement Tuesday saying McGuinty's resignation at a time of economic uncertainty raises concerns that Ontario may not be able to balance its books by 2017-2018 as planned.

"The premier's resignation and prorogation of the legislature during a time of heightened global economic risks, in our opinion, introduce some uncertainty over the province's fiscal targets in the medium term," S&P said in a statement.

"In our view, increased uncertainty within the context of a minority government may raise the prospect of a delay in Ontario reaching fiscal balance by its fiscal 2018 target."

People on the streets of Toronto were surprised by McGuinty's resignation and had mixed views on his move to prorogue the legislature.

"I don't like prorogation ... on the other hand, it gives them breathing space so they can choose someone to replace him," said Melville Olsberg, 80.

"I think from that point of view, they made a wise move. Otherwise, it would just be chaos at Queen's Park."

David Blackmore, 55, said he was "very disappointed" that McGuinty prorogued the legislature.

"I know he's tired that it's an embattled government, but to close down the government during these crucial times, I don't think it's the right thing to do," said Blackmore.

"I would urge him to reconsider and bite the bullet, say I made a mistake, open government back up."