TORONTO - Ontario's government is intentionally hiding information about the impact the 13 per cent harmonized sales tax will have on gasoline when it comes into effect July 1, the New Democrats charged Tuesday.

Finance Minister Dwight Duncan knew the facts when he told the legislature that he didn't know the extra cost the average Ontario motorist will face because of the HST, which will add eight per cent in tax to the retail price of gas, said NDP Leader Andrea Horwath.

"The minister is deliberately withholding the basic facts about the HST," Horwath told the legislature. "People have the right to know how much the HST is going to cost them, and he has that information."

The NDP gave reporters copies of a freedom of information request it made last June to find out what studies the government had showing the projected impact of the HST on energy costs, documents the government wasn't willing to give up.

Releasing charts, graphs and summaries on the HST "could give rise to a negative effect on consumer confidence and lead to a decrease in consumer spending, thereby adversely affecting the economy," was the response, repeated seven times, in a letter denying the NDP the documents.

"Does this minister really believe that telling people how much more it's going to cost them at the pumps could actually bring Ontario to the edge of economic collapse, or is it more about protecting the interests of the governing party," asked Horwath.

The government's tax package, which also includes cuts to corporate and personal income taxes, will help create 600,000 jobs over the next decade, said Duncan, who blasted the NDP for taking the freedom of information documents out of context.

"All they can do is take one line out of one document where they remove the date, torque the answers and ignore the largest personal tax cut for lowest-income Ontarians in the history of this province," Duncan told the legislature.

"Even her own document, had she read the rest of it, said this is about a whole package of tax cuts and other initiatives."

The province has been up front about the fact 17 per cent of consumer goods will rise in price under the HST because it will apply to items currently exempt from Ontario's provincial sales tax, including gasoline, home heating fuel and electricity, said Premier Dalton McGuinty.

"We've provided more information than any government ever has before it presented a harmonized sales tax to its population," said McGuinty. "We presented all kinds of information online, including specific case scenarios."

The Liberal government is so confident the HST is the right thing for the province's economy it is implementing it in the last year before an election, added McGuinty.

"We're not running on putting the HST in place after the next election," he told reporters. "We're going to put it in place before the next election so people can see it and then understand what this means in terms of the 17 per cent of products that will receive an additional level of taxation."

The Progressive Conservatives said the Liberals don't want to release the HST impact studies because they're aware that many people know very little about the HST at this point.

"It's largely gone under the radar up until now," said Opposition critic Christine Elliott. "I think people are really starting to figure out what it's going to cost them, and the more they hear about it the less they like it."

Last month the NDP released documents obtained under freedom of information legislation showing the HST would add $225 a year to the cost of heating and electricity bills for the average Ontario home.