Ontario Premier Dalton McGuinty is defending extra costs to consumers under the HST. (Darren Calabrese/Canadian Press)

Premier Dalton McGuinty admits Ontario families will pay more in taxes because of the HST, but says the new tax is vital to help businesses compete.

The New Democrats released a study showing families will pay hundreds, if not thousands of dollars more in taxes once the 13 per cent harmonized sales tax starts July 1.

McGuinty says the HST will help Ontario businesses compete in the global marketplace, and he's asking people to pay more to help create jobs and a better future.

The premier says he believes he's doing the right thing, and notes people will be able to make a call on that in next year's election.

NDP Leader Andrea Horwath says McGuinty is shifting taxes from businesses to families, which she believes is the wrong approach when people are still hurting from the recession.

The Progressive Conservatives say the HST is the wrong tax at the wrong time.