Several dissident directors of the Diplomat National Bank have charged that other board members leaked confidential financial plans of the bank to the Office of the Comptroller of the Currency and that the bank regulators acted improperly in forcing the bank to finalize plans for its sale last month.

The charges, which have been referred to the inspector general of the Treasury Department, surround the controversial takeover of the bank by Leo M. Bernstein, the former vice chairman of National Savings and Trust Co. and a long-time District businessman who won control of Diplomat last month.

In addition, the complaint charges that Bernstein "had a special relationship" with the comptroller's office "due to his many years in commercial banking." Bernstein, the complaint said, met with officials of the comptroller's office "to discuss purchasing control of the bank before he even officially made his interest known to the bank.

"Further, Mr. Bernstein emphasized this relationship as being a positive factor that the bank should consider in deciding whether to accept his offer," the complaint said.

Bernstein, who was reached yesterday at Diplomat offices, pointed out that he had been in business in the District of almost 50 years and had worked with government agencies throughout much of that period. He denied that any inappropriate influence had been used in arranging for his purchase of the bank.

The complaint was submitted by Nando Difilippo, an attorney for the directors, including the bank's former chairman, Dr. Soo Young Oh, and another director, Waldemar Solf.

The bank originally set up in 1975 in part to provide services for the area's Asian-American community, has never turned a profit and fell into even more difficult circumstances when it was linked to Korean influence-peddling scandals and, according to the complaint, operated between September 1977, and June 1978 "without any effective management whatsoever."

The bank problems became so acute that the comptroller, charged with maintaining bank solvency, signed a consent agreement with Diplomat, which force the bank to raise $1 million.

But the dissident directors said in the complaint that government officials said the deadline "would be extended reasonably to allow" the comptroller to approve of the transaction under the Change in Bank Control Act.

The bank's board accepted Bernstein's offer to pay $2 million for 500,000 shares of the Diplomat stock July 15, rejecting a $1 million offer for 250,000 shares of the Diplomat stock by a Korean institution, the Cho-Heunk Bank.

The ultimate sale to Bernstein has drawn complaints from some members of the Asian-American community. In fact, former chairman Oh has written to Gilbert Colon, a White House deputy assistant for minority affairs, to complain about their loss of control of the bank.

Now Oh has taken his complaints about the directors and the comptroller's office to the Treasury Department. The complaint charged that, although the bank's board had agreed to keep the details of negotiations secret until the capital plan was in final form, "at least one director favorable to Mr. Bernstein's offer may have violated his fiduciary duty to the bank."

The unwillingness of the comptroller's office to extend the deadline for the financing deal "in effect was to veto the board's selection of the Cho-Heung purchase group and to force it to accept Mr. Bernstein's offer," the complaint said.

"This constituted a gross and flagrant abuse of the authority delegated to the OCC [Office of the Comptroller of the Currency] by Congress," the complaint concluded.