Ontario's Liberal Party was under heavy fire on Thursday as its political rivals looked to make hay on the final stretch of the provincial election campaign.

The New Democrats continued to attack Liberal Leader Dalton McGuinty for his party's sudden decision to cancel an unpopular plan to build a gas-fired power plan in Mississauga – a move both the NDP and Progressive Conservatives have attacked as a politically-motivated flip-flop.

NDP Leader Andrea Horwath wrote to the auditor general and asked for the plant closure to be investigated. In a letter released to the public, she said it is important to know what impact the decision to stop construction on the site will have on taxpayers.

Horwath said an investigation was necessary because the Liberals would not say how much it would cost to cancel the plans, and because the Liberals pulled a similar move in Oakville last year.

"We've been asking for (the cost) but we haven't been getting it," Horwath told reporters in Toronto. "That's the problem."

The Liberals say they were listening to constituents in the area when they decided to scrap the power plant and move construction to an as-yet-undecided location.

Progressive Conservative Leader Tim Hudak joined in Horwath's attack, accusing the Liberals of scrambling to make up new policies in the days leading up to the Oct. 6 election.

McGuinty, meantime, said in Pickering on Thursday that he would introduce a tax credit for home renovations 15 months earlier than the Liberals had previously planned, in the hope that it would help boost job creation ahead of a financial slump.

He said the credit would create demand for skilled labour, similar to how a comparable federal program helped the country recover from the last recession.

"It will take effect on Oct. 1, at a time that will inspire, I believe, greater confidence in the people of Ontario and help create better jobs," McGuinty told reporters on Thursday.