Riggs National Bank increased its profits by 20.1 percent last year, earning a net income of $18.3 million as loans and deposits hit record levels.

Riggs Chairman Vincent C. Burke Jr. said the improved profits came "across the whole panorama of our operations: consumer, commercial, real estate, construction -- it was an extraordinary year for construction loans in Washington -- and international, were all up."

The biggest bank in the District of Columbia, Riggs reported earnings before securities transactions of $18.5 million ($6.12 a share) up 21.6 percent from the $15.26 million ($5.04) earned in 1977.

After securities transaction losses of $219,000, Riggs had net income of $18.3 million ($6.05) up from $15.26 ($5.04) last year.

For the fourth quarter ended Dec. 31, Riggs reported net before securities losses of $4.93 million ($1.62) up 9.2 percent from the $4.51 million ($1.49) earned the same period a year earlier. After securities losses for the quarter, net income was $4.71 million ($1.55) compared with $4.51 million ($1.49).

The operating results include Riggs' banking operations and its wholly owned subsidiary, Central Charge Service Inc. Riggs does not report separate results for Central Charge but Burke said, the credit card business was a "a plus" though not a major factor in Riggs' total operation.

The consumer credit operation has been pinched by high interest rates, he pointed out.Central Charge customers pay 12 percent interest on their balance over $500 while the bank's prime rate charged the best corporate customers is now 11 3/4 percent.

Other lending activities, however, became more profitable as interest rates went up to near record levels.

Riggs' rate of return on stockholders equity -- a key indicator of bank performance -- jumped 1.5 percentage points to 12.9 percent in 1978 from 11.4 percent the previous year.

At year end, Riggs assets were up 17.2 percent to $2.4 billion from just over $2 billion, deposits were up 16.7 percent to just over $2 billion from $1.7 billion and loans were up 24.2 percent to $1.1 billion from $929 million.