Registrations of political action committees fell to the lowest level in three years in 1990, although fund-raising groups representing industry grew slightly, the Federal Election Commission said Saturday.

The commission, in a semiannual survey completed Dec. 31, counted 4,172 committees raising and spending money to influence federal elections, down 21 from the 4,193 committees registered July 1.Total PACs have declined steadily since a peak of 4,268 at the end of 1988, broken only by a gain of 15 committees posted during the first six months of last year, the commission reported.

Corporate PACs remained the largest category with 1,795 committees, followed by non-connected groups at 1,062, trade groups and health issues with 774 committees and labor PACs numbered 346, the report showed.

Industry committees rose from the 1,782 posted at midyear but remained below the peak of 1,816 committees registered at the end of 1988, the report showed.