Homeowners are going to be "shocked" when they learn how much their property assessment has soared, Ontario's Opposition Leader John Tory said Thursday.

He said property values have gone up dramatically over the last three years during the time Premier Dalton McGuinty imposed a freeze on property assessments.

"Everybody across the province, when you have three years of pent-up assessment increases that haven't shown up on the papers, everybody is going to be shocked at the numbers and in many cases it will lead to tax increases which people can't afford right now -- plain and simple," he told reporters.

Although the premier acknowledged the property tax assessment system is not perfect, McGuinty said he would not reconsider lifting the freeze.

"We think it would be unfair to too many to delay the inevitable," he said at a news conference. "At some point in time there has to be a property tax assessment system which is in effect and that's what's going to happen now."

Here are some examples of how much properties have gone up in value over the past three years:

  • In the GTA, detached home values are up 20 per cent
  • The value of a home in Rosedale has gone up 42 per cent
  • In Oshawa, homeowners have seen their property value soar by 14 per cent

McGuinty said there is a plan to help seniors who face dramatic increases. He also stressed that property taxes will not necessarily go up as much as the property assessment.

Toronto Mayor David Miller said he's worried about people who can't afford much of an increase at all. He said the system is designed in a way where people are punished because their houses go up in value.

"When the cap comes off some neighbhourhoods, some people will face some challenges," he said. "It's a system that means if you live in a popular neighbourhood you pay more. Some other neighbhourhoods pay less in taxes, their taxes go down. That's what the assessment does."

Tory said one way to help ease the shock of the soaring assessment is by capping increases at 5 per cent.

Homeowners are expected to receive their property assessments by late summer.

With a report from CTV Toronto's Paul Bliss