THE resignation of two Washington powerbrokers - Clark Clifford and Robert Altman - may seem parochial when considering the massive international banking scandal now unraveling.But the development is an important thread in the intricate tapestry woven by the Bank of Credit and Commerce International (BCCI), the $20 billion institution that until recently operated in some 70 countries. Last month banking regulators around the world moved to shut down BCCI in their respective jurisdictions. BCCI officials are suspected of fraud, bribery, drug trafficking, running arms, and financing the development of nuclear weapons. This week's resignation of Mr. Clifford and Mr. Altman, since 1982 the two highest-ranking officers of First American Bankshares, is the result of mounting pressures from legislators, prosecutors, and federal officials now investigating the Washington bank holding company. Investigators say First American was illegally acquired by BCCI a decade ago and since then has been secretly controlled by the bank. Mr. Clifford, a lawyer/lobbyist, former United States defense secretary, and pillar of the Democratic Party, stepped down on Monday from his post as chairman of First American. Altman, his young prot who rose quickly through the ranks of Washington's business elite, also resigned as president of the bank company. The two, who remain senior partners in the prestigious law firm of Clifford and Warnke, have denied any wrongdoing. They reject investigators' allegations that they were aware of BCCI's financial control of First American or that BCCI had managerial influence over First American's day-to-day operations. But investigators point to Clifford's and Altman's more complex and long-term relationship with BCCI, dating back to their legal representation of the bank in 1978. The probers say they suspect the two of using their connections with government of-ficials to lobby on BCCI's behalf. The Federal Reserve Board has found that Clifford and Altman made millions of dollars in a 1988 stock deal involving a Caribbean company that BCCI illegally controlled and that they bought the stock with a BCCI loan. The two men are now at the center of a controversy over why the federal government apparently failed to properly investigate BCCI's illegal network in the United States. A former top federal official, congressional investigators, and New York District Attorney Robert Morgenthau have pored over bank documents, accumulated evidence, and interviewed witnesses for the past three years. They say their findings have been systematically ignored by federal authorities. Former Customs chief William von Raab orchestrated an October 1988 sting operation implicating BCCI as a drug-money launderer and then spearheaded efforts to bring extensive indictments against the bank and its officials. He says his work was blunted by the US Treasury and Justice Departments, which eventually removed him from the case, citing "overzealousness." According to BCCI's former chief financial officer, Masihur Rahman, BCCI engaged the law firm Clifford and Warnke to "unwind" the Tampa money-laundering case and counter federal charges. Mr. Von Raab calls the Justice Department's ensuing plea bargain with BCCI a slap on the wrist. Von Raab faults the federal government for subordinating concerns over BCCI's criminal activity in the US to the Justice Department's need to squeeze BCCI for evidence in a case it was building against Panama strongman Manuel Noriega. This, coupled with BCCI's influence peddling in Washington, he says, kept the federal authorities from approaching a BCCI investigation with the same zeal as his own. Sen. John Kerry (D) of Massachusetts leads the congressional investigations into BCCI. Chairman of the Senate Foreign Relations Subcommittee on Terrorism, Narcotics, and International Operations, Mr. Kerry has blasted the Justice Department for creating obstacles to his committee's BCCI investigation on the pretext that the federal authorities were conducting one of their own. The Justice Department only recently launched its own investigation, several years after the October 1988 plea-bargain agreement in Tampa. Asked why Justice has been slow, Kerry says "the bombardment of lobbying" and the Noriega case figure prominently. He plans to explore this further in hearings next month when Congress returns from August recess. Both Clifford and Altman are scheduled to testify before his committee on Sept. 5. Mr. Morgenthau's office - replete with jurisdiction (BCCI signed a contract purchasing the National Bank of Georgia in New York, for instance), a skilled fraud division, and prosecutorial power - has given the BCCI case the push it needed, says Kerry. Morgenthau's office has already slapped BCCI and its top officials with indictments alleging that they schemed to defraud depositors. Upcoming indictments will involve alleged BCCI criminal schemes against US regulators, probably including federal and state governments in Washington, D.C., New York, Maryland, Tennessee, Florida, Virginia, Georgia, and California. Asked about former Attorney General Richard Thornburgh's insistence that the Justice Department is cooperating fully with Morgenthau, a source close to the Morgenthau probe says, "If anything, Justice has impeded the investigation," withholding evidence requested by Morgenthau. A prominent international banker, who calls his industry's trade "Byzantine and complex," says the current climate leaves too much potential for abuse, and regulators are intimidated. "Banking's too important to leave just to bank regulators, but it's also too important to leave to lobbyists and the politically well-connected," says the banker. "The fact that respected expertise is available for hire, vouching for these guys, makes it very tough for politically poorly connected regulators to do their job right." Senator Kerry agrees. "BCCI represents the degree to which Washington sort of looks the other way, doesn't hold people accountable, doesn't try to apply the same standard to everybody."