HARRISBURG -- Within 10 days, some conservative Republican legislators say they'll introduce a measure that would lower the state's sales tax from 6 percent to 4 percent but also greatly expand the list of goods and services that are taxed.

The GOP group, called the Commonwealth Caucus, released a study yesterday estimating that an additional $10 billion a year would be raised under the broader sales tax -- money they said would be used to eliminate school property taxes statewide.

Under the group's sales tax proposal -- which is still subject to change -- the only goods or services that would be exempt from the 4 percent levy would be gasoline and prescription drugs plus services provided by hospitals, nonprofit groups and tax-exempt institutions.

Even if the controversial proposal were enacted, it wouldn't take effect until mid- or late 2005, said state Rep. Samuel Rohrer, R-Berks, a leader of the Commonwealth Caucus with Rep. Mario Scavello, R-Monroe County.

Items that would, for the first time, be subject to a 4 percent sales tax include food bought at supermarkets, clothing and shoes, natural gas, oil and electric utility costs, newspapers and magazines, caskets, candy, flags and services by doctors, lawyers, accountants, engineers and other professionals.

Rohrer told a news conference yesterday that he's hoping for discussion on the proposed 4 percent sales tax -- as well as a vote in the GOP-controlled House -- by June 30, when lawmakers break for the their summer recess.

He said the proposal probably won't be discussed in the state Senate until the fall, but he's shooting for enactment by the Nov. 2 election or else by the end of the current session Nov. 30.

It wouldn't take effect for nine months, he said, to give businesses and residents a chance to get used to the changes.

House Majority Leader Sam Smith, R-Punxsutawney, cautioned that not all the Republicans in the General Assembly have endorsed this plan, but he said they do want to get further information "to help them make an informed decision. We have an obligation to examine all possible solutions relative to tax reform that might help Pennsylvania residents.''

The Commonwealth Caucus measure has been strongly criticized by Democratic legislators as unfair to poorer people, who spend a greater portion of their family income on food and clothing, which are now exempt from sales tax. Whether the 4 percent sales tax plan would be vetoed by Gov. Ed Rendell, a Democrat, isn't known yet.

House Democratic Leader H. William DeWeese of Waynesburg blasted the GOP plan yesterday.

"Senior citizens, families and people at the lower end of the socio-economic ladder will get hammered by this," DeWeese said. "They'll have to pay taxes on food and clothing they haven't had to pay before.''

DeWeese supports bringing slot machines to Pennsylvania and taxing that revenue to raise $1 billion to use in cutting property taxes. He said the sales tax changes are "just an attempt to muddy the waters and divert attention from gaming.''

Rohrer was asked if state legislators would really be willing to vote, in an election year, to extend the sales tax to food and clothing. He acknowledged the plan has its critics, but said its major benefit is raising $10 billion in additional funding to allow the elimination of school property taxes around the state.

He said that lower-income homeowners pay a large part of their income on school property taxes and would benefit from eliminating them. The main segment of people who might not benefit much, he conceded, are low-income renters, because they don't pay property tax. But they still could benefit from stabilization or even reduction of their rent that lower property taxes would make possible, he contended.

Rohrer said a considerable amount of time is needed to study this proposed tax change, which he called "the most sweeping tax policy change the state has ever undertaken.''

Rohrer's group released a study yesterday by an Orlando, Fla., financial consultant called Fishkind & Associates. It estimated that about $9 billion in additional revenue would be collected from the broader, but lower, sales tax.

The plan also includes a companion tax proposal -- increasing the state's realty transfer tax to 4 percent from the current 2 percent, a move estimated to raise an additional $1 billion a year.

If the Legislature decided to grant more exemptions to the revised sales tax -- thus costing the state some revenue -- the new rate for the tax might have to be 4.25 percent or 4.5 percent, Rohrer said. Such discussions will be held in the House Finance Committee and then the full House in June, he said.