Metro's expanding subway and bus system showed as dramatic 23 percent jump in ridership from December of 1977 to December of 1978, General Manager Theodore C. Lutz told the Metro Board yesterday.

That percentage, which represents an increase in average daily ridership from 391,342 to 480,094, is the most impressive statistical jump Metro has shown since it began opening subway lines and rerouting bus service to feed the subway in March 1976.

The big jump occurred during a period that saw the addition of both the Silver Spring and New Carrollton extensions to the subway and the beginning of weeknight and Saturday subway service.

But ridership was climbing anyway. From May to November of 1978 -- a period that saw one month of nighttime service and four Saturdays but no new lines -- ridership increased 10 percent.

Most significantly, Lutz said in his quarterly ridership report to the board, bus patronage "has recovered from the downward slump which occurred after the opening" of the subway's Blue Line in July 1977.

Average daily ridership on an annual basis has also been increasing steadily, the report shows. For example:

Average Daily Ridership

Fiscal 1975... 376,525

Fiscal 1976... 399,775

Fiscal 1977... 413,479

Fiscal 1978... 435,723

The numbers count a trip involving both bus and subway as one teip.

The increases in ridership have been largely anticipated in Metro's budget process and will have little effect on the $98.6 million operating deficit of the system in the current fiscal year. For example, Metro is now projecting that the subway will make about $5.5 million more than was expected, but that the bus system will lose $5.3 million more than was expected.

Despite the growing popularity of the subway, the bus system continues to be the big hitter in the region's transit picture. It also requires about two-thirds of the total operating subsidy that lical jurisdictions pay for Metro.

In November, for example, average daily rideship on Metrobuses was 381,333, while the subway was carrying an average of 215,374 people.

The ridership increases appear to be continuing, particularly through the past few difficult weeks. The subway's one-day ridership record of about 270,000 was set on Feb. 5, the first day of the tractor protest here. Since that time, weekday ridership has averaged more than 260,000. The three days of lost subway service due to the Great Sonowstorm appear to have had little effect on ridership. On Feb. 22, when the subway returned to service, it carried about 259,000 people.

Lutz was clearly delighted with the news he gave the board, and he used it to make one more pitch for the inauguration of Sunday subway service, something he wants to start.

"Considering the energy situation and our harsh winter," Lutz said, "I'm hopeful we'll be able to work this out."

The board's budget committee received reports yesterday morning from most local jurisdictions on Metro's proposed fiscal 1980 budget, which offers Sunday service as an option. The District of Columbia strongly backed eight hours of subway oh Sunday, and most suburban jurisdictions said they would support Sunday service if the impact on their property taxes was not too great.

The board is scheduled to make a final decision on the fiscal 1980 budget in about two weeks. However, the Sunday subway issue will be decided after public hearings, which Metro has scheduled for later this month primarily to set fares.

At yesterday's Metro board meeting, Walter Frankland, the new board member from Arlington County, cast his first negative vote -- against advertising a construction contract. Frankland in the past has opposed completing the Metro system.

The contract, estimated at $160,000 to $180,000, is for a small electrical power station on the Shady Grove line. That line, an extension from Dupont Circle, is totally funded under a binding contract among the federal government and seven local governments. The line is scheduled to open in 1983.

Frankland said that "it is time for the board to seriously reconsider the redirection of this money" to other purposes.

He specifically suggested the 14th Street bridge Metro crossing, which is unfunded but a top priority in a new funding package Metro is attempting to assemble. Frankland was defeated, 5 to 1.