An article in the Business & Finance section yesterday incorrectly reported the date on which the 11-member Interstate Commerce Commission must be reduced to five members. The commission would have to be reduced to seven members immediately and to five members by 1986.

Rebuffing last-minute pleas from the White House, the Senate yesterday voted overwhelmingly to reduce the size of the Federal Communications Commission from seven to five members, eliminating posts the Reagan administration wanted to fill with its choices.

By a 71-27 vote, the Senate refused to accept an amendment by Sen. John P. East (R-N.C.), that would have kept the FCC a seven-member commission. Refusal came after White House Counselor Edwin Meese and other administration officials argued that the commission should be kept at seven members to allow President Reagan to appoint Stephen A. Sharp, currently FCC general counsel, to the commission.

At the same time, however, the Senate agreed to an amendment that will permit the Interstate Commerce Commission to operate with seven members until 1985, a move that could protect the job of controversial ICC Chairman Reese H. Taylor Jr.

The amendments were attached to an omnibus budget bill.

The ICC amendment was a victory for Sen. Paul Laxalt (R-Nev.), a former law partner of Taylor. Without the change, Taylor would have had to step down from the commission at the end of 1983, when the agency was slated to be reduced from 11 to five members.

Under the amendment, Taylor will be able to stay at the commission until Dec. 31, 1984, if the president reappoints him when his term expires at the end of next year. As of 1985, however, the commission will be cut to five members.

Taylor had argued that any move by Congress to limit his term would have hurt his effectiveness as ICC chairman. Yet congressional sources say that senators were not persuaded by this argument, especially because many are unhappy with the slowness with which Taylor is moving to deregulate the trucking industry. Rather, sources say, the Senate voted for Taylor as a favor to Laxalt.

But the votes were not there for Sharp, whose biggest backers include East, Sen. Jesse Helms (R-N.C.), FCC Chairman Mark Fowler and the Rev. Jerry Falwell.

By reducing the number of seats on the FCC from seven to five by June 1983, Sharp would be limited to serving less than a year's term on the commission. Reagan had nominated him to a seven-year term earlier this summer.

Meese and other White House aides, in a series of last-minute phone calls to senators, argued that cutting the commission would be unfair to Sharp, whom they cite as a top-notch appointment.

But Sharp was strongly opposed by the Senate Commerce Committee, which has made it clear it will oppose his appointment, largely because one of its members, Sen. Ted Stevens (R-Alaska), had backed another candidate from his home state.

Even Sen. Barry Goldwater (R-Ariz.), a member of the committee, opposed the White House yesterday, and told other senators on the floor to vote against East's amendment. Goldwater and the committee argued that the reduction would save the government money and make a more effective commission.