Former Arlington legislator Ira M. Lechner said yesterday he will continue his bid for the Democratic nomination for lieutenant governor of Virginia even though a party committee has rejected his challenges to nearly 1,000 delegates pledged to an opponent.

"I'm not giving up, but I'm realistic enough to know I'm going uphill," said Lechner, who this weekend lost challenges to the race's front-runner, Richard J. Davis, Lechner, a Washington labor lawyer, has alleged that Davis, a former state chairman, employed fraudulent campaign practices and "Watergate-style dirty tricks" to win delegates to the party's nominating convention.

The party's temporary credentials committee, however, rejected Lechner's complaints over nearly 1,000 Davis delegates picked in an estimated 60 jurisdictions. In most cases, Lechner charged that local organizers had violated a state party rule requiring public notice 10 days in advance of local mass meetings.

Lechner's supporters also withdrew challenges to more than 500 other Davis delegates in 30 jurisdictions after party officials supplied copies of notices dated at least 10 days before the meetings were held.

According to party figures, Davis is within 125 delegates votes of winning his party's lieutenant governor nomination at the May 29 convention in Virginia Beach. He has 1,686 of the 1,806 convention delegates he needs. Lechner, in a surprisingly strong showing, garnered 1,119 delegates at meetings around the state last month, and state Sen. Dudley (Buzz) Emick of Fincastle won 166. There were 518 uncommitted delegates selected. e

Lechner said yesterday he will press his challenges on the floor of the party's nominating convention. Davis supporters have characterized Lechner's charges as "frivolous," and say they will make no differences in the balloting.

Lechner charged that the party's 15-member credentials panel had exercised "no semblance of fairnes" in its decision, but C. Phillips Ferguson, Suffolk commonwealth's attorney and a committee member, countered that Lechner had shown a "lack of judgment" because he "filed charges without regard to whether there was any truth to them or not."

"The committee rejected them on the grounds that there was no favoring of any campaign over another," said Ferguson. Any lack of meeting notices was ". . . at most inadvertence or oversight. There was no evidence that his people had been prejudiced by it," Ferguson said.

In the only other contested state race on the Democratic ticket, Dels. Gerald L. Baliles and Erwin W. (Shad) Solomon have both pronounced themselves the likely first-ballot victor in their contest for the attorney general nomination. The key to that race appears to be in the hands of 1,153 uncommitted delegates, many of whom are pledged to Lechner and hope to use their lack of commitment to a candidate as leverage for Lechner.