The general counsel of the troubled National Bank of Washington, Ronald G. Nathan, has resigned from his post and from the bank's board of director, the bank's chief executive, Dale Jernberg, said yesterday.

Nathan, whose Washington law office said he was in New York and unavailable for comment, also has been a lawyers for factions of the United Mine Workers of America. The UMW is NBW's principal shareholder.

Nathan also is an investor in an energy investment venture involving another former bank director, Bruce Lyons, a partner in the troubled local real estate firm of Holland & Lyons Associates Inc. The gas well venture received a $1 million loan from the bank.

Lyons resigned from the NBW board earlier this year in light of Lyon's holding of more than $3.6 million in loans to the bank, most of which were delinquent.

These transactions and a series of other questionable loans to bank director and others are the target of both internal and grand jury investigations. Both sets of probers are looking into the loans and the influence the UMW may have over the bank's operations.

Jernberg, the bank's chairman and president, said Nathan's resignation became effective on Aug. 4, Nathan did not give the reasons for his resignation in the letter, Jernberg said.

In 1978, Nathan's firm, which was then known as Nathan & Mause, received more than $91,000 in legal fees from the bank. Last year, Nathan, who is now with Kadison, Pfaelzer, Woodard, Quinn & Rossi, received close to $200,000 in legal fees from NBW.

Jernberg also said the bank's internal investigation -- which is being conducted by Gibson, Dunn & Crutcher, another local law firm -- would be completed and presumably presented to the bank's board of directors within 10 days.

Jernberg said it would be up to the board to determine how much, if any, of the internal report would be released to the public.

Among the transactions under investigation is a $4.5 million loan to Joseph E. Shamy, a New Jersey developer, who used the money to refinance the then-Laurel Raceway in Maryland.

When the loan was approved, Shamy already had defaulted on an earlier loan made to purchase primary interest in the race track and was the target of a federal investigation for misappropriating track funds. He was later convicted of those charges by a federal court in Baltimore.