Virginia Gov. Charles S. Robb warned yesterday that he may order further cuts in state spending this year on top of the 6 percent across-the-board reductions already in effect.

Robb said in a message to the House Appropriations Committee that early indicators show that state revenues will fall short of the $3.3 billion needed to balance the second year of Virginia's 1983-1984 biennial budget.

" . . . It now appears that it will become necessary to lower the 1984 estimates and concurrently reduce our expenditures," the governor said. "Consistent with my belief that, while we should hope for the best but must prepare for the worst, I've asked my staff to develop contingency plans for keeping the budget in balance."

Although Virginia ended fiscal 1983 with a tiny surplus, collections from several major taxes fell below anticipated levels. The state income tax produced $35 million less and corporate taxes $1.3 million less than anticipated. Those deficits were made up in part by an unexpected $21.2 million increase in the state sales tax.

The dip in state revenues, combined with a cautious outlook for a sustained economic recovery this year, prompted Robb to call for a revision of the revenue forecast for fiscal 1984. He told legislators yesterday that those new estimates will be available next month.

Until those figures are updated, state officials yesterday said they could not come up with a dollar figure on the anticipated shortfall or with any specific proposals on where the state budget can be further cut.

"At this point, we have not attempted to analyze those figures," said state budget director Stuart Connock. "What we're doing now is trying to forewarn the General Assembly that there is a good possibility that we will have to do something this year and that if we don't, we may not be able to balance the budget."

Del. Richard Bagley (D-Hampton), chairman of the House Appropriations Committee, said yesterday it was too early to tell what kind of cuts would be necessary. "I have not had a chance to see by way of impact in dollars what the governor's words meant," he said.

Bagley said the revenue figures vindicate the budget cuts already in place. "If we had not already taken the steps we have to reduce expenditures, we would indeed be in trouble," he said.

Faced with a deepening recession, Robb last year ordered an initial 5 percent across-the-board cut in state spending in 1983, which was then followed by another 6 percent cut in the second half of the biennial budget.

When collections were counted at the end of the fiscal year in June, revenues for 1983 exceeded original estimates by $1.6 million, the slimmest margin in years, several state officials said yesterday. Another $13.8 million was returned unspent by state agencies, but Robb said those funds will be reserved for emergencies.

Connock yesterday said that one cause for the drop in collections from the state income tax was the popularity of Individual Retirement Accounts, which siphoned off $21 million in state income taxes last year.