In an unusual union bargaining tactic, a Washington labor group yesterday disclosed it has asked the U. S. comptroller of the currency to turn down a request by Hemisphere National Bank to open a new branch in Adams Morgan.

The Food and Allied Services Trades Metro Washington Council charged the branch would provide few services to neighborhood residents and accused Hemisphere executives of having a secret financial interest in the bank's expansion plan.

The council -- known as FAST -- filed a formal objection to Hemisphere's branch application, noting that more than 1,000 union members live in the neighborhood and another 600 work in the area.

FAST's president is Thomas McNutt, president of Local 400 of the United Food and Commercial Workers, which won an election last spring to represent 16 Hemisphere Bank employes.

So far, Local 400 has been unable to negotiate a union contract with the bank, the first Washington financial institution to be organized by the union.

Hemisphere Chairman Leveo Sanchez called the union tactic "harassment" and said he expects the new branch to be approved despite the union objection because "there's no substance to it."

Organized as a minority bank catering to the Latin American community, Hemisphere wants to open its first branch at 18th Street and Columbia Road NW, because that is the heart of Washington's Hispanic community, Sanchez said.

"Many of our customers already live there," he said. "We speak the language; more than half our employes are bilingual."

The union charged that many Adams Morgan residents won't be able to use the bank because Hemisphere requires a $250 minimum to open a checking account, more than neighborhood people can afford. The labor group also complained that Hemisphere has made few home-improvement loans and mortgages and therefore is not serving the community as required by federal regulations.

Sanchez said most Washington banks have avoided mortgage lending because of unstable interest rates and disputed union charges that bank officers had a financial interest in the branch.

The labor group said Hemisphere board member Adelina Callahan owns property across the street from the proposed branch and would profit by the bank's investment in the neighborhood.

Chairman Sanchez is also chairman of Development Associates Inc., the consultants hired by Hemisphere to study new branch locations, and should have disclosed that position to the comptroller, the union said.

The group also questioned the adequacy of the bank's internal auditing, noting that Peter B. Davis, a board member who serves on the audit committee, is also president of Development Associates.

"It is difficult to believe that Mr. Davis can objectively perform his duties as a member of the committee while at the same time serving in a professional position outside the bank in which he is responsible to Mr. Sanchez," the labor complaint said.