TORONTO -- Ontario's Liberals hope to turn their minority government into a majority in two byelections this fall, Premier Dalton McGuinty said Wednesday following the resignation of former finance minister Greg Sorbara.

"I take heart in knowing that he's still going to lead our effort in our campaign to secure a strong, stable majority," McGuinty said after Sorbara announced his retirement as the MPP for Vaughan.

With some of his children and grandchildren watching, Sorbara -- his wife Kate at his side -- stood with McGuinty to announce he wanted to devote more time to his family, but would also stay on as co-chair of the Liberals' election campaign and head of their fundraising arm.

"Given the realities of minority government and the possibility of an election at any time the opposition parties chose to defeat the government, a great deal more needs to be done to prepare for an early election," said Sorbara.

"I feel it's important to see to that mission, developing policies for that campaign, recruiting candidates for the ridings that we don't hold, and raising the money necessary to...contest and win that election."

McGuinty has until October to call a byelection in Kitchener-Waterloo to replace veteran Progressive Conservative Elizabeth Witmer, who quit after the premier appointed her to a $188,000 post as chair of the Workplace Safety and Insurance Board in April.

Both the Kitchener-Waterloo byelection and the one in Vaughan to replace Sorbara will be held at the same time, and sometime after Labour Day, McGuinty said.

"I just don't think it would be fair to vote during the course of the summer," he said.

"I think we should allow Ontarians...to enjoy their summer, but having said that, I think we are in a sooner-rather-than-later mode."

McGuinty said he's not worried the opposition parties will hammer the Liberals over their wage dispute with teachers or the $190 million cost of cancelling a Mississauga power generating station during the byelection campaigns.

"They'll use whatever they choose to use, and we stand to be judged in these byelections as we are as we do in general elections," he said.

"We're prepared to defend any decisions we made."

Sorbara, who was first elected in 1985, said his proudest achievement -- besides helping the Liberals defeat the Conservative government in 2003 -- was the introduction of a Child Tax Benefit, which provides low-income families with up to $1,100 per child each year.

However, he will also be remembered for introducing a health tax of up to $900 for every worker in the Liberals' first budget.

Sorbara quit cabinet a few years ago after being McGuinty's right-hand man in finance, but remained an influential adviser to the premier and co-chaired the Liberals' re-election campaigns.

Sorbara's resignation came after three previous attempts to quit the life of an elected politician, said McGuinty.

"He's come to me at least three times in the past and said, 'I've got to get out of this place. I've got to devote more time to my family,' and I said to Greg: 'You can't. I need your energy. I need your idealism. I need your passion,"' said McGuinty.

"Well there comes a time, as they say, when Greg's got to fish or cut bait, and he has decided that he is going to put his family first. I respect that."

The Tories praised Sorbara's public service, but said he was part of a Liberal government that racked up a record deficit and nearly doubled Ontario's debt in nine years.

"The fact is this province is in a mess; we have a jobs crisis and a fiscal crisis," said Conservative Rob Leone.

"I think the people of Vaughan and the people of KW need to hear that message."

The New Democrats stayed on the high road, thanking Sorbara for his years of public service and holding any criticisms for another day.

"While we may not always have seen eye to eye on the floor of the legislature, I appreciate Mr. Sorbara's determination and skill," said NDP Leader Andrea Horwath.

Sorbara's resignation leaves the Liberals with 52 seats, one fewer than the combined Progressive Conservatives and New Democrats.