Riggs National Corp. laid off more than 50 employees yesterday, eliminating at least one department and bringing to about 200 the number of Riggs staff members who have lost their jobs since June 30, according to sources close to the bank company.

Yesterday's layoffs capped months of cutbacks at all levels of the bank and are part of an overall cost-cutting effort that is expected to reduce Riggs's work force by 10 percent, or about 250 workers, by the end of the year, sources said.

Riggs is the second company controlled by Joseph L. Allbritton to cut back employees this year. Earlier this fall, WJLA-Channel 7, a division of Allbritton Communications, laid off about 20 employees, citing concern that the soft economy would reduce advertising revenue. Sources said those layoffs and the reduction at Riggs, where Allbritton owns 35 percent of the stock, reflect Allbritton's pessimistic view of the local economy.

"He watched Houston's demise, and he's certain that the same thing will happen here," said one source at Riggs, who asked not to be identified.

Allbritton, who came to Washington from Texas in 1974 and still has a home in Houston, was the first Washington area banker to publicly warn of the slowdown in the area's commercial real estate market. A conservative businessman, he stopped making commercial real estate loans at Riggs in late 1988, months before other banks and thrifts in the area.

Despite his precautions, Riggs -- the largest bank based in the District -- has been hit hard by the area's slumping commercial real estate market. Sources said Allbritton is looking for ways to shore up 1990 profits. Troubles with its commercial real estate loans have eroded Riggs's earnings by more than 75 percent in the first nine months of this year, and a recently completed review of the bank's loan portfolio by federal regulators is expected to further hurt earnings in the fourth quarter.

Sources said nearly every bank department will be affected by the layoffs by year-end, except for Riggs's profitable trust department and its commercial real estate department, which is busy restructuring past-due real estate loans.

Riggs spokesman David Palombi confirmed that any staff cuts are part of a broad program to reduce expenses, but he declined to discuss details of the layoffs except to say that affected employees are receiving severance pay and placement assistance.

Yesterday's layoffs wiped out mainly the bank's 30-person sales department for its cash management services. The staff had been marketing Riggs's cash management services to prospective small business clients. "There were no warnings or anything," said one salesperson, who asked not to be identified. "They just called us in and told us we weren't needed anymore. They said they didn't want the business."

Palombi said Riggs will continue to offer cash management services.

Other employees who ultimately will be affected include accountants, recruiters and operations personnel, who help process checks and perform other administrative chores on bank accounts, sources said.

Riggs is the latest in a series of banks and savings and loans, including Perpetual Savings Bank, American Security Bank and Chevy Chase Federal Savings Bank, to lay off workers to compensate for large losses or plummeting profits.