South Korean evangelist Sun Myung Moon's Unification Church continues to own a controlling interest in Diplomat National Bank of Washington and is selling some of its holdings without properly informing new investors, the Securities and Exchange Commission charged yesterday.

Currently, the SEC alleged in a suit filed in U.S. District Court, representative of Unification Church International own one-third of the stock in Diplomat, a minority bank chartered here in 1975 to serve a growing Asian-American community.

At one time, according to government allegations filed earlier and again yesterday, the church and South Korean agents secretly owned half of the bank's stock.

Representatives of Moon's organizations immediately denounced the SEC action as "discriminatory enforcement of securities laws." John M. Bray, a Washington lawyer for Unification Church International, said he will file a motion in court today seeking to dimiss the charges as "a suspicious repetition of prior action" involving the SEC and alleged South Korean investors.

Cathy Lowrey, a spokeswoman for the Unification Church at its headquarters north of New York City, said that the SEC's action would appear to contend that because several investors in a bank happen to have the same religious persuasion, "they are the same as agents of the church."

Since the SEC has not similarly moved against persons of other faiths who may happen to have common stockholder interests in other banks, "to apply such a standard . . . is no less a violation of our rights," she stated.

To settle a 1977 suit by the SEC, Diplomat Bank agreed to stop all activities cited by the regulatory agency and to expand its board of directors, without admitting or denying that there had been any violation of law.

At the same time, the SEC order required that former chairman Charles Kim be dismissed from bank management and that the controlling South Korean investors could not exercise their voting rights as shareholders.

Although many of the SEC allegations yesterday duplicated earlier charges of how the Unification church "participated in a scheme to obtain undisclosed control" of Diplomat Bank, the major thrust of the new case is that bank control by the church continues and that this has not been disclosed properly.

The suit yesterday was filed against Unfication Church International, a non-profit Washington corporation established in 1977 to coordinate all activities of the church. Lowrey emphasized that this firm is not tax-exempt and that it is distinct from the purely religious organization, incorporated in California in 1961.

According to the SEC complaint, Unification Church International participated since 1975 in a "scheme" to gain control of Diplomat Bank. SEC officials would not comment on the apparent discrepancy between the 1975 date in the allegation and the incorporation of the firm in 1977, but Unification lawyer Bray charged that the agency appears to be "stretching to attach liability."

At issue is the initial offering of Diplomat Bank stock, in which the bank said no one person would be permitted to own more than 5 percent of all shares. Officers of the bank have stated that they do not know of any person that owns more than 5 percent but the SEC charged yesterday that:

Unification Church International controlled or attempted to control Diplomat policies by management of its checking account at the bank, "which at times constituted approximately 30 percent of Diplomat's total deposits."

Acquisition of loans from Diplomat, exceeding the bank's legal lending limit, was approved for a corporation related to Unification Church.

Beginning in September 1976, during the resale of Diplomat stock on behalf of alleged Unification Church nominees, "misrepresentations and omissions were made to purchasers and prospective purchasers pertaining to" continued church checking accounts at Diplomat.

Specifically, the SEC alleged that Unification Church International had up to $2.5 million in a non-interest-bearing account from February 1976 to May 1977, and that this was increased by a $2 million deposit at the end of 1977, just prior to a year-end report to federal bank regulators and at a time when the bank's board was divided on whether to retain Kim in an important capacity.

Separately, a Diplomat director and outgoing vice chairman, Diosdado M. Yap, has charged that 10 of 12 persons nominated to the bank's board at an annual meeting of stockholders last night are "close to" or "pro" Kim, the former chairman.

According to yesterday's SEC complaint, Kim aided the alleged secret takeover of Diplomat Bank, located at 2033 K St. NW. In an interview, Yap said that although Kim is not formally associated with the bank at this time," his influence remains."

Yap said that at a recent board meeting, he was ousted by a 6-4 vote through a decision to establish a mandatory age limit of 70 for directors. Yap, 72, is president of a Washington firm, Capital Publishers Inc., which produces guidebooks to Congress and other books.

Yap said he decided to speak out because his role as director includes "protecting the people." He charged that the South Koreans continue to control the bank through actual stock ownership and domination of the bank's board.

Diplomat President Thomas J. Leonard III, who took over as chief executive last year in a management shakeup mandated by federal bank regulators, denied Yap's allegations in an interview last week.

Last night, following the annual meeting, Leonard said "nothing of major interest" developed at the session, which was closed to reporters. Leonard said yesterday's SEC suit was not discussed at the meeting. " . . . We have no knowledge of anything . . . we are not a party to the suit," said Leonard, who first learned of the SEC complaint from a reporter.

According to Leonard, stockholders elected two new directors, physicians Thomas Chun and Hyo Keun Lee. They replace Yap and Charles C. Yu. Another board member, physician Soo Young Oh, was elected vice chairman to succeed Yap.

Of 17 commericial banks in D.C., Diplomat ranks 16th in total deposits, which were $7.8 million on March 31.