ANNAPOLIS, JAN. 23 -- Major business and welfare advocates today endorsed a proposed restructuring of Maryland's tax system, among the most significant support to date for the proposal.

In separate statements, the Maryland Chamber of Commerce, the Greater Baltimore Committee and a loose coalition of social service groups endorsed the recommendations of the Commission on State Taxes and Tax Structure, headed by Montgomery County lawyer R. Robert Linowes.

However, the support was not unconditional.

The Greater Baltimore Committee, representing 1,000 Baltimore-area businesses, endorsed the entire plan as a step to ensure the city's health.

The chamber, meanwhile, supported many of the commission's ideas but ruled out major tax increases because of the recession. Tax restructuring, the chamber said, should be "revenue neutral" instead of raising the $800 million envisioned by the Linowes commission.

The anti-poverty groups, whose constituents are beginning to feel the pinch of state budget cuts, pledged to lobby for the plan but want some of the additional money committed to programs for the poor.

But taken together, Linowes and aides to Gov. William Donald Schaefer said, the endorsements indicate that the tax-overhaul coalition they have been trying to build is taking shape.

"This happens with everything that appears to be impossible: You build it with little pieces," said Daryl C. Plevy, a lawyer and adviser to Schaefer. "Part of what you are building is a climate for accepting change."

"There are going to always be disagreements over what resources you hit and whose ox you gore," said Linowes, referring to the chamber's decision to endorse the plan's philosophy while opposing tax increases.

Faced with generally negative reactions from lawmakers, Schaefer has withheld introducing legislation and instead has had Linowes and administration officials concentrate on building support among civic and issue groups, educators and business leaders.

Next week, Linowes will begin appearing before key General Assembly committees, while administration officials are counting on the Feb. 1 release of Schaefer's budget to soften lawmakers on the idea of a tax increase. The budget will be the tightest in years, with deep program cuts that, Schaefer aides say, only a tax increase could abate.

The Linowes plan would raise $800 million, most of it by increasing the sales tax from 5 to 5.5 cents on the dollar and by extending it to services. Also, a 2 percent annual personal property tax would be applied to cars and boats.

The bulk of the additional money would go to school and road projects, with the emphasis on Baltimore and other low-income areas.

The chamber's decision to back major parts of the plan is a particularly encouraging development, Linowes and Schaefer administration officials said. The business community has been seen as a possible stumbling block.

The Washington Board of Trade has not taken a position on the plan.

"We think it is a terrific report and is the basis of thinking for years to come on how we should change things," said Ron Creamer, chairman of the state chamber. The chamber endorsed the idea of making income taxes more progressive but rejected any increase in the sales tax.

After an address today by Linowes in Annapolis, some anti-poverty advocates were skeptical that much of the new revenue would reach low-income people.

"Sure, it is a leap of faith to assume" low-income people's needs will be funded, said Lynda Meade of the Maryland Alliance for the Poor. "It is a risk we have to take."