The Government Employees Insurance Company, which a month ago began a volunteer effort to untangle the District of Columbia's confused voter registration records, has completed the task with the compilation of a list of 291,000 names -- about 28,000 more than were on a list released recently by the city -- sources said yesterday.

The earlier list was put together by staff members of the city's Board of Elections and Ethics and contained about 263,000 names. City officials were not available to explain the difference, but they said earlier that they believed the District of Columbia actually had about 280,000 eligible, registered voters. .

Elections Board chairman Albert J. Beveridge III acknowledged that the Geico figure "was around 291,000" but declined further comment. He said he would make a formal announcement about Geico's work on Monday.

Sources close to the Geico project said that the insurance firm found that more than 200 computer tapes of registered voters existed instead of the 137 that initially were reported.

"The elections office didn't even have an index" of the tapes, one official said.

Geico took on the project April 1 after a City Council committee investigation found that nearly 50,000 voters could have trouble casting ballots in September's primary elections because of inaccurate, incomplete and missing registration records.

The investigation was begun last November after the city reported massive foulups on election day that kept many persons from voting and caused long delays for others.

Beveridge said yesterday the elections board would try to consolidate the lists by May 14, when candidates for mayor and City Council are required by law to begin circulating petitions to have their names placed on the ballot. The number of signatures each candidate must obtain will be based on the number of registered voters listed.

Rep. Julian C. Dixon (D-Calif.), chairman of the House Appropriations subcommittee on the District of Columbia, told Beveridge during a hearing on the city's budget yesterday that the city was "lucky there were no hotly contested races" last fall.

"I think it would be disastrous if there were any question as to the integrity of the voting system," Dixon said. Beveridge assured Dixon the city was trying to avoid major problems this year. He noted that the city recently had hired Teddy Filosofos, a former Erie County, N.Y., elections official, as head of the city's elections office. Filosofos has said that he would stake his reputation as a "no-nonsense" administrator on September's balloting.

Meanwhile, E. Brooke Lee, a candidate for the Republican mayoral nomination, announced that he had filed suit in U.S. District Court in an effort to require the city to reregister all voters before the September balloting.

The history of election foulups is unconscionable, Lee said. "It is a denial of my and every other District resident's constitutional rights. Here in the world capital of democracy, the most crucial aspect of a democratic system -- one person, one vote -- is being abridged by incompetence."