Shareholders of Riggs National Bank yesterday voted to form a bank holding company -- an expected move that puts the area's largest financial institution in a position to expand regionally if Congress permits interstate banking.

Immediately after the annual meeting Joe L. Allbritton, who recently took control of the bank, was elected chairman of the executive committee of the board of directors. Allbritton and his associate Thomas W. Wren, who heads an Allbritton bank in Houston, were elected to the bank's 25-member board by the shareholders.

Riggs Chairman and Chief Executive Officer Vincent C. Burke, who was re-elected to those jobs, announced during the meeting that the comptroller of the currency has approved an application by Riggs for two new branches, one at 12th and Pennsylvania Ave. NW and another at 6th and Pennsylvania Ave. SE. The application had been opposed by a group that said it was objecting on behalf of the community.

The former owner of the Washington Star, who controls an empire worth more than $200 million, rose only twice during the meeting -- once to be recognized as a director, and another time to offer a resolution commending the bank's officers, directors, shareholders and customers.