Virginia Gov. Charles S. Robb is planning a new wave of budget cuts to cope with a sudden decline in state revenue collections caused by the recession.

Citing what he called "dismal economic conditions," Robb said today that he now anticipates cutting deeper than the $55 million across-the-board 5 percent spending reduction he imposed this summer after state planners projected a major revenue shortfall. Although Robb refused to specify the amount or areas targeted for reduction, state officials said they now believe this year's shortfall will be even worse than the $75 million "worst case" scenario projected last May.

"It is very serious," Robb said after a speech to state agency heads. "I don't want to paint for anyone an optimistic figure of revenue forcasts."

The governor's comments came a day after new revenue figures were presented to the House Appropriations Committee by state budget director Stuart W. Connock. Those figures showed that revenue collections actually declined in the month of October compared with the same period in 1981. The state's total revenue intake was $214 million, or 3.6 percent less than a year ago.

"October looked terrible," Connock said today. "It was the worst month we've had so far."

The decline in October was principally caused by drops in income and sales tax collections -- the state's two chief money producers, both of which have been crimped by the recession. Connock blamed the state's 7.4 percent unemployment rate which, although lower than the national figure of 10.4, is nonetheless unusually high for Virginia's traditionally recession-resistant economy.

The problem of coping with a slumping national economy was the principal theme of Robb's speech to agency directors. He outlined stringent spending guidelines in planning for the state's 1984-1986 biennial budget. Raising the possibility that the country could be facing a "continued and prolonged economic recession or even a depression," Robb said he will continue his informal state hiring freeze that has already resulted in a reduction of 1,500 state employe positions since he took office.

Specifically, he said, he will require "that any employment initiated by an agency for new services be offset by an equivalent reduction in employment for existing services so that our overall size and shape doesn't increase -- at a minimum."

In addition, gubernatorial aides handed out hundreds of copies of a glossy new 61-page booklet, "Virginia -- A Future Worthy of Her Past." It spells out Robb's policy goals for the upcoming budget. Among the goals emphasized is a broadening of public "user fees" to pay for specific state services and restrictions on construction projects.