CITY COUNCILMAN Mark Squilla plans to introduce legislation Thursday to phase in over four years the jaw-dropping changes in homeowners' property taxes that come with the Actual Value Initiative.

Squilla, the latest Council member to try to blunt the impact of the city's new property-tax system, said the measure also would give the city's Office of Property Assessment time to address concerns about some home values.

"I think there's a lot more mistakes than OPA realizes," Squilla said.

Some members are concerned, however, that phasing in the tax changes would mean that those who have been overpaying for years would have to wait too long to get their full tax break.

"Over several decades, large chunks of the community have overpaid, and to continue to suffer for a period of time doesn't sit well with me," said Councilman Curtis Jones Jr.

Councilman Wilson Goode Jr. agreed: "Those who have been unfairly assessed for years should not have to pay more for those who have been underassessed."

Mayoral spokesman Mark McDonald said that the Nutter administration will comment at a hearing, which hasn't been scheduled.

The administration proposed a similar idea last year called "smoothing," which would have phased-in increases only.

Squilla represents the 1st District - one of the hardest-hit under AVI - which includes Fishtown, Northern Liberties and Center City.

He said that everything needs to be on the table. Several relief measures will be debated in Council this spring.

Kevin Gillen, research consultant with the University of Pennsylvania Fels Institute, said Squilla's bill would require a higher tax rate, though Squilla disagrees.

"It will delay the day of equity," Gillen said, adding that the bill could provide grounds for legal challenges.

"There are measures to help people. I'm not sure phasing [AVI] in is the best way."