TORONTO - The campaign for the Oct. 6 Ontario election is quickly turning into a battle over taxes, with the opposition parties attacking the Liberals over the HST, which they say has made life more unaffordable for voters.

The New Democrats promised Thursday to remove the harmonized sales tax from home heating oil, natural gas and hydro bills if they win the election, and would scrap $850 million a year in corporate tax cuts to offset the lost revenue.

"The HST is simply a shifting of tax burden off the corporate sector onto the backs of individuals," said NDP Leader Andrea Horwath.

"We would claw back the corporate tax cuts the government has implemented and cancel the future ones."

Scrapping such a big slice of corporate tax cuts would hurt the fragile economic recovery by raising taxes on the struggling forestry and automotive sectors, warned Finance Minister Dwight Duncan.

"It is about the most short-sighted, dumb public policy pronouncement one can envision," said Duncan.

More than 100,000 people have signed the NDP's online petition, started in September, to remove the HST from hydro bills. Taking the HST off of home heating fuels may be just the next phase of more changes to come, hinted Horwath.

"As we move over the next couple of months, you'll get a more clear picture of exactly what we're going to do with the whole HST piece," she said. "We're not at that position yet to release our platform."

However, Horwath wouldn't say if the NDP would eventually promise to remove the HST from gasoline, lower the rate of the tax or even scrap it completely, a move that would cost the province $4.5 billion to cancel its tax agreement with the federal government.

"Is it possible tomorrow? (It would) cost a lot of money," said Horwath.

"Is it possible three years from now? Maybe it'll cost a little bit less then. So there are things that we need to look at in terms of us costing that scenario out."

The Progressive Conservatives, meanwhile, said "everything is on the table" when it comes to providing tax relief for voters, but like the NDP, won't be pushed into releasing their campaign platform.

"Our platform will be released when we're ready to release it ... not when Dalton McGuinty tells us to," said Opposition critic Peter Shurman.

Remaining vague is unfair to voters and the Tories should stop playing coy and start telling people now exactly what they would do differently, said Duncan.

"People will smell a rat, and that's a rat," he said.

"Mike Harris had the courage to put his platform out more than a year before the election. Obviously (PC Leader Tim) Hudak hasn't got the courage or the strength of character that Mike Harris did."

The Tories say they would not cancel the planned corporate tax cuts, which are worth $1.4 billion this year and $1.8 billion in 2012-13.

"If you're going to provide tax relief on any level you have to have something that's equal and opposite, so when it comes to corporate tax cuts I think what's needed right now is some stimulus so that business expands in Ontario," said Shurman.

The Liberals defend the HST as a necessary measure to make Ontario businesses more competitive, which in turn is supposed to make the province more attractive to investors and help create hundreds of thousands of new jobs.

"I think as much as most Ontarians probably don't like it, I think they understand it," said Duncan. "And I think they can see through pandering, which is what I've heard over the last 48 hours."