The trial of a lawsuit seeking to collect about $24,000 in back taxes and penalties on waterfront property owned by a partner of Alexandria Mayor Frank E. Mann will be delayed until after the mayoral election because of what was decribed yesterday as a City Hall "slip-up."

"The order [for a trial] wasn't entered when it should have been," said City Attorney Cyril D. Calley, whose office prosecutes city tax suits. "I guess this case has been delayed a little longer than it should have been. It was a slip-up, it fell through the cracks," said Calley.

The election will be held May 1; the suit will be scheduled for trial during the first week of May, said Calley,' a Democrat. Mann, a Democrat-turned-Independent, is in a hard-fought contest with Charles E. Beatley, a Democrat.

The subject of the mayor's involvement with the delinquent property taxes is becoming a controversial subject in the campaign. On Monday evening Mann was questioned several times about the subject during a campaign debate with Beatley at Del Ray Citizens Association meeting.

The topic has been simmering in Alexandria since last fall, when the city threatened suit against John C. Richard, the mayor's friend and partner in the unincorporated Port of Alexandria company, which owns the land. The suit names Richard and the company because their names are listed on real estate records.

According to city records, Richard and the company have paid virtually no taxes since 1974 on the eight-tenths of an acre waterfront parcel between Prince and Duke streets. The total amount due is $23,546.23, according to records from the City Finance Department.

On several occasions Mann has said at City Council meetings that a longstanding federal suit challenging title to waterfront land has led the company to withhold taxes. Mann has also said that the firm had never received tax bills, an assertion city officials have questioned.

Last September Mann told the council that "against my wishes" Richard are was placing the full amount owed in an escrow account until the issue could be resolved. Yesterday Richard said that the escrow account, at the First Commonwealth Saving & Loan Association, in Alexandria, contained the $23,546.23, plus several thousand dollars more to cover upcoming taxes and potential penalties.

Under the escrow arrangement, the money cannot be touched without the agreement of the city attorney, Richard said.