His written statement capped a day in which Liberals had been scrambling to contain the damage from his ill-timed remarks, which came just days before a byelection in Calgary, where the Liberals have high hopes for an upset.
"I would like to unreservedly and unequivocally apologize for comments which I made with respect to parliamentary colleagues from the province of Alberta," said McGuinty, whose brother Dalton is premier of Ontario.
"My words in no way reflect the views of my party or leader and I offer my apology to them, as well as to my colleagues from Alberta.
"I hold all parliamentarians in high esteem and I regret my choice of words, as I can understand the offence they have caused."
Earlier Wednesday, Interim Liberal Leader Bob Rae said McGuinty's comments were a mistake, frankly admitting they could hurt the party's byelection chances.
"Obviously, it's not helpful," he said following the Liberals' weekly caucus meeting.
"That's why I'm saying, unreservedly and without qualification, I apologize. It doesn't reflect my views, it doesn't reflect my approach to this issue, it doesn't reflect the way in which I would address it or describe it, it doesn't reflect my view of how MPs do their job ... I think it was a mistake."
Conservatives, who polls have suggested were in trouble in the Calgary Centre riding where Monday's byelection is taking place, pounced on McGuinty's comments.
Four Alberta MPs rose before question period to demand his resignation and denounce his remarks — typical, they said, of a party long biased against Alberta since the 1980s, when former Liberal prime minister Pierre Trudeau imposed the National Energy Program.
Even Prime Minister Stephen Harper, whose own riding is next door to Calgary Centre, got in on the act, using a response on an unrelated matter to go after the Liberals.
"I find it shameful — I guess not surprising, but shameful — that 30 years after the National Energy Program, these anti-Alberta attitudes are so close to the surface in the Liberal party," Harper told the Commons, to boisterous cheers from the Conservative benches.
Alberta, and Calgary in particular, have been politically toxic for the Liberals since the imposition of the NEP. Liberals have been trying to live it down ever since.
Trudeau's eldest son, Justin, the front-runner in the current Liberal leadership contest, has taken pains to disown his late father's energy policy. He was on a campaign swing in Alberta on Tuesday when news of McGuinty's comments first surfaced and he quickly distanced himself from his colleague.
"My entire campaign has been about bringing people together, about not pitting region against region," Justin Trudeau had said in Edmonton.
On Wednesday, he went further and called McGuinty's comments "unfortunate," but said he didn't believe they would sway voters in the Calgary byelection.
"We need to be a national party and what Mr. McGuinty said was regretful, but I think that the people who decide 'that's all the Liberal Party is good for,' probably weren't going to vote for us anyway," he said at an appearance in Victoria, which also votes in a byelection Monday.
"It ticks me off as a Liberal. I think it was an unfortunate thing to say."
Trudeau had visited Calgary Centre on Tuesday to campaign for Liberal candidate Harvey Locke, whom polls have suggested is running a close second to Conservative candidate Joan Crockatt. The Tories have held the riding for more than 40 years.
When asked if he would've demanded McGuinty's resignation if he was party leader, Trudeau said he would have a "very serious conversation about how effective that member could continue to be in as important a role as natural resources critic when he had expressed those views."
The controversy arose Tuesday after a meeting of the Commons natural resources committee, which was devoted to a study of energy innovation.
McGuinty accused Conservative MPs from Alberta of being "shills" for the oil industry, particularly Alberta's oil sands.
"They really should go back to Alberta and either run for municipal council in a city that's deeply affected by the oil sands business or go run for the Alberta legislature," he told a reporter for Sun Media outside the committee room.
Rae, who spoke privately to McGuinty early Wednesday, said the MP assured him he hadn't intended to insult Albertans.
"I don't think (the comments) really reflect what he was trying to say. I think that he was expressing some exasperation with the difficulty of getting the committee to look at a national approach on energy. I think the way that he expressed himself was unfortunate," he said.
"I don't think he intended any offence to anybody but it certainly came out that way."
Immigration Minister Jason Kenney, who also represents a Calgary riding, said the vast majority of Albertans find McGuinty's comments "deeply offensive." He reminded McGuinty that Alberta's energy industry is responsible for almost 20 per cent of the country's gross domestic product and creates hundreds of thousands of jobs.
"For a Liberal MP to tell other MPs to get lost, to leave Ottawa, that their democratic mandate is somehow tainted or illegitimate for defending their constituents, is deeply offensive and I would ask Mr. McGuinty and his party to apologize for these remarks."
Kenney said he can't recall McGuinty ever suggesting that separatist Bloc Quebecois MPs should go back to Quebec because they were representing their constituents' interests.
"But he seems to apply a double standard to Albertans, which is the long track record of his party after all."
NDP natural resources critic Peter Julian, who was at Tuesday's committee meeting, said he has no idea what set off McGuinty.
The NDP has denounced Harper's government for aligning itself with the interests of the oil industry, at the expense of the environment. But Julian said that's different from suggesting Alberta MPs have nothing to add to the debate.
"Comments that attack any region of this country are not helpful," Julian said.
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