International Bank of Washington, a holding company that invests in diverse financial services and industrial businesses, yesterday reported a 29 percent decrease in earnings for 1980 and a 55 percent drop for the fourth quarter.

Earnings for the year ended Dec. 31 were $13.1 million ($1.06) compared with $18.5 million ($2.53) with the average number of shares at 12,351,231 compared with 7,326,921. Revenues were $22.8 million compared with $26.0 million.

For the fourth quarter, net income was $2.6 million (20 cents) compared with $5.8 million (79 cents). Revenues were $4.6 million compared with $7.6 million.

International Bank Chairman George Olmsted said that during the year the bank "contended with spiraling inflation, skyrocketing interest rates, depression in the automotive and construction industries and recession-level unemployment."

Virginia Electric and Power Co. yesterday announced earnings for the 12 months ended Feb. 28 of $245.0 million ($1.94) compared with $199.3 million ($1.63). Revenues were $2.1 billion compared with $1.8 billion.

Vepco President William W. Berry attributed the higher annual earnings to increased sales caused by abnormal weather, increased use of nuclear and coal generating units and reduce use of oil-fired generation.

Potomac Electric Power Co. reported earnings for the 12 months ended February 28 of $91.9 million ($2.16) compared with $74.2 million (1.79). Operating revenue was $893 million compared with $752.7 million.