The national governing board of Common Cause moved yesterday to defuse a sharp controversy within the 225,000-member group, delaying action for three months on a major reorganization that would reduce its activities in individual states.

Backers of the reorganization, which would fold 40 state offices into about a dozen or so regional ones, said it was necessary to cut costs and end duplicate fund-raising in a "time of reduced resources."

Many of the group's state affiliates, led by Virginia, charged that the change would "emasculate" them and was being "rushed through."

After a 12-hour committee meeting Friday and a five-hour board meeting yesterday, the governing board voted 45 to 4 for the three-month delay. It said the time would be used to work out voluntary cooperative arrangements between state groups and allow a new committee to work out another reorganization plan.

In the meantime, it said total spending by the state groups would be cut about 25 percent.

Founded in 1970, Common Cause reached its peak membership of 325,000 in August 1974, the month President Nixon resigned because of Watergate.

The income of the national lobbying group that year was $6.5 million but is has dropped to about $5.3 million a year, as interest has waned in the group's chief issues, campaign financing and government ethics.

Its founder, former Health, Education, and Welfare secretary John Gardner, stepped down as chairman in 1977. He took part in yesterday's board meeting at the International Inn on Thomas Circle NW and strongly endorsed the delay.

After he spoke, Kathleen Sebelius, head of the committee that proposed the reorganization, said she supported the delay, too.

"To be anything in Common Cause," she said, "you have to be able to quote John Gardner and win."