With the HST set to start applying on Canada Day, Ontario's opposition politicians used the opportunity to highlight how they say it will hit families.

Outside a gas station on Wednesday, Progressive Conservative Leader Tim Hudak noted that people should gas up before midnight as the price at the pump will rise eight per cent on Thursday.

The price at a Jarvis and Richmond Streets Petro-Canada was 96.4 per cents per litre as he spoke. Liberal MP Dan McTeague, who studies gas prices, predicted a price of 104.4 cents per litre on Thursday.

"We all know that the day before Canada Day is already an expensive day at the pumps," Hudak told reporters.

"The HST will just make it worse as families try to get away for a holiday weekend."

Service stations are bracing themselves for a run on gas, he said, urging people to fill up before the new, 13 per cent tax applies and "takes a big bite out of their wallets."

CTV Toronto's Paul Bliss said that Hudak hinted to reporters he might repeal the tax if his party takes power after the October 2011 provincial election.

The HST harmonizes the old eight per cent Retail Sales Tax with the federal five per cent GST, leading to the higher rate.

The 13 per cent rate already applies to about 83 per cent of Ontarians' purchases, the government has estimated.

Gasoline wasn't covered by the Retail Sales Tax. As a result, its price will rise under the HST.

Bliss said Hudak also suggested a Tory government might reduce the HST to 12 per cent, but he didn't commit to that possibility.

At Queen's Park, the NDP showed reporters their HST countdown clock.

NDP Leader Andrea Horwath said the new tax will make life less affordable for most Ontarians.

The federal Conservative government gave the provincial Liberals $4.3 billion to distribute as HST transitional payments.

In the 2009 provincial budget, the government also announced income tax cuts.

However, it has admitted that middle-income households will notice a small bite out of their budgets -- about $45 per year. Lower-income households will come out ahead, while high-income households will pay more in tax.

Revenue Minister John Wilkinson told CTV Toronto that the new tax system, which only taxes businesses on their value-added output, has been adopted by 130 countries.

Businesses in those countries have a cost advantage over Ontario businesses as a result, he said.

"Everywhere around the world where they've done this, it's led to lower prices," Wilkinson said.

Businesses here will eventually pass savings on to consumers, but Wilkinson admitted that will eventually take time.

With reports from CTV Toronto's Paul Bliss and Pat Foran