RICHMOND, DEC. 13 -- Virginia Gov. L. Douglas Wilder said today the state's budget shortfall has swollen by another half-billion dollars, and his aides reported that more layoffs and spending cuts in education, social services and other programs are on the way.

After meeting with senior legislators, the governor announced that projected tax collections are down by $491 million more than he had predicted three months ago, bringing Virginia's lost revenue to $1.9 billion. The shortfall could continue to grow, Wilder said, if Virginia merchants have a poor holiday season, reducing sales tax receipts.

The growing shortfall, caused principally by a weakening state economy, will prompt a new round of spending cuts that Wilder has yet to detail. His press secretary, Laura Dillard, said it is possible that as many as 350 state workers will be laid off, which would bring to 1,100 the number of positions eliminated so far in Virginia's budget crunch.

In Maryland, Gov. William Donald Schaefer has called for the elimination of 1,800 jobs to help cover a $423 million deficit.

Virginia state agencies drew up contingency plans last month to cut spending in the remaining 18 months of the two-year budget cycle by an additional 7.5 percent, and it is virtually certain now that these plans will be implemented. Most already had trimmed spending between 5 percent and 10 percent.

The new cuts, which Dillard said may be revised before being approved by Wilder, would eat away at a vast array of services offered by state government. Legislators said today that the earlier cuts already have left some programs and agencies at the breaking point.

"We're going to be decimating some programs," said Del. Leslie L. Byrne (D-Fairfax). "Some of the departments that were tenuous to begin with are just being destroyed."

King E. Davis, commissioner of the state's mental health department, said a proposed $5 million cut for his agency would prompt 100 layoffs and could lead to at least one of the state's mental hospitals losing its accreditation.

The mental health agency, target of some of the most publicized cuts in Wilder's earlier reductions, already has cut about 175 positions and eliminated a care facility for older mentally ill persons at Western State Hospital in Staunton that served many Northern Virginia patients.

Dillard said programs under Education Secretary James W. Dyke Jr. -- including public colleges and universities and financial aid to local public schools -- were targeted for $80 million in cuts in the contingency plans.

Local school districts already have been targeted for $135 million in aid cuts for next fiscal year. Legislators said the latest budget numbers are likely to lead to further aid cuts.

The figures announced today do not reflect transportation taxes, such as the tax on gasoline, which are accounted for in a separate part of the budget and are the primary source of road construction funds.

Transportation Secretary John G. Milliken said those figures are "not good news" either, and that when they are announced, they likely will mean further delays in the state's construction schedule.

Wilder today repeated his opposition to tax increases.

"Taxpayers and businesses all across Virginia are having to tighten their belts and even forgo purchases and services they would like to have," he said in a statement. "I believe the same standard ought to be applied to state government and that we ought to live within our means."

Wilder aides, however, hinted that the governor is becoming more flexible on another subject on which he had been unyielding: spending a $200 million reserve fund that he proposed and the General Assembly approved last winter.

The reserve fund "is designed for an uncertain economic situation," said Dillard. "That's what we're in."

Wilder is scheduled to outline his plans for covering the shortfall before the General Assembly's money committees on Monday. The central question facing the legislature when it convenes in January is whether it will go along with the governor's proposed cuts or come up with its own.

"I think there's going to be an attempt by the legislature to come up with our own priorities," Byrne said.

News of the latest cuts was especially unwelcome for Northern Virginia, where localities face the prospect of reduced state aid at the same time their own fiscal pictures are darkening.

But Prince William County Supervisor Edwin C. King (D-Dumfries) said local officials are under the same political pressure to avoid tax increases as Wilder. Although the latest news is bad, King said, "We'll take up another notch or two on the belt."