The D.C. Board of Elections and Ethics will seek emergency help from a private firm to untangle jumbled registration records that could ensnarl the September primary elections, officials said yesterday.

Board chairman Albert J. Beveridge III said Mayor Marion Barry has agreed to make a "reasonable amount of money available" to pay for compiling new lists of registered voters from old computer tapes and as many as a million registration cards, most of them outdated, filed away in the board's offices.

Beveridge, who said he was not sure how much the project would cost, said he would immediately begin contacting private firms. He said he hoped the project could be completed within 60 to 90 days.

The recommendation of outside help came from the City Council's government operations committee, which revealed in a public hearing two weeks ago that as many as 50,000 people could have trouble voting in the Sept. 14 primary because of inaccurate, missing or incomplete registration records.

According to a consultant hired by the committee, the elections board currently has no way of knowing precisely how many voters there are in the District. Officials said an approximate figure would be 280,000.

The council committee, in an interim report on its hearings released yesterday, also said the current elections staff should concentrate solely on current additions to and subtractions from the voting rolls until the special project is completed.

The committee recommended the outside firm go back as far as 1978 registration records to produce a master computer listing of registered voters, which would then be cross-checked by volunteers.

Beveridge said he would seek help from Advisory Neighborhood Commissions, the League of Women Voters and other groups to review registration lists compiled by the outside firm.

The committee recommended that the outside help come from a large concern with experience in computer operation and large-scale record keeping.