A proposal by Northern Virginia governments that would eliminate the cut-rate bus fares Metro now offers riders who avoid rush hour was attacked last night at the first in a series of hearings on proposed fair increases.

For many years Metro has given its bus riders a break if they rode the bus at midday, at night and on weekends. Philip Swift of Falls Church testified last night that if that policy is abandoned his fare from where he lives to downtown Washington would increase from 80 cents to $1.65.

Keith Konradi, also of Falls Church, said the proposal "is out of line."

Northern Virginia governments have proposed three different fare schedules that could take effect June 29. The proposal to eliminate the so-called off-peak fare is defended by Northern Virginia transit planners as a "simplification" and is proposed in only one of the three schedules.

For most rush-hour riders in Virginia, combined bus and subway fares would increase from between 5 to 40 cents, depending on the residence of the rider and the fare table adopted.

The complexity of the proposals was attacked by several witnesses at George Mason Junior-Senior High School in Falls Church last night.J. E. James of Fairfax City asked, "did an Internal Revenue Service man design this? I'd like to have about 18 hours to study this; then maybe I could understand this. Why can't we have a simple fare?"

Two citizens complained last night about erratic bus service on their 3W route, which runs from Tysons Corner to the Ballston Metro station.

Sandra Vies said the bus comes only 70 percent of the time and asked why. Richard Walter, who boards the bus earlier than Vies, said it sometimes makes the wrong turn and takes a different route, which explains why Vies might be missing it. "Why do you deserve such a large (fare) increase when we're getting such bad service?" Walter asked.

Joseph Alexander, a member of both the Fairfax County and Metro boards, directed Metro staff members to solve the 3W problems.