The Metropolitan Washington Labor Council voted last night not to endorse a candidate for D.C. mayor as members split their support almost evenly between Mayor Marion Barry and Patricia Roberts Harris. At the same time, the members endorsed David Clarke by overwhelming voice-vote in the race for City Council chairman.

Last night's endorsing convention of the city's unified labor leadership had been expected to produce the first showdown over a major endorsement between Harris and the mayor because of the financial contributions, campaign workers and potential votes it usually brings.

The vote to back no mayoral candidate, however, came after a single ballot on which both Barry and Harris fell far short of gaining the two-thirds majority needed to win endorsement. The vote was 294 for Barry, 289 for Harris, with most of the public-employe unions supporting the mayor and most of the private-sector unions supporting Harris.

The labor council's executive board, dominated by public-employe union officials who are pleased with contracts they recently negotiated with Barry, earlier had urged the council's 250,000 members, including 90,000 who live in Washington, to support Barry's reelection.

"We got one of the best contracts the last time out," explained Bernard Demczuk, an organizer and lobbyist for the American Federation of Government Employees (AFGE). "Whether it's the election year or a political ploy, we don't care. He has produced for us."

Harris supporters, including members of the building trades, operating engineers and hotel and restaurant workers unions, contend that Barry betrayed labor by supporting changes in the city's workers compensation and unemployment insurance laws that benefit Washington businesses.

They also objected to his layoff of hundreds of city workers and complained that he permitted nonunionized employes to work on the Convention Center project.

"These regressive acts can be laid at the doorstep of big business's Washington representative--Mayor Marion Barry," said J.C. Turner, president of the International Union of Operating Engineers and a former president of the labor council in a telegram to members who attended last night's convention at the Capital Hilton Hotel.

"I urge you, in the name of solidarity and trade unionism, not to let Barry get a single union vote because he is not our friend; he is our enemy and the enemy of all workers in this city," Turner added.

Supporters of Harris, who is considered Barry's chief opponent in the Sept. 14 Democratic primary, also claim she deserves to be elected because she resisted attempts to rescind or dilute the Davis-Bacon Act, which requires federal contractors to pay higher wages than they otherwise might on public projects when she was secretary of Housing and Urban Development (HUD) in the Carter administration.

Barry's supporters, including members of the AFGE and the American Federation of State County and Municipal Employees (AFSME), have scheduled a press conference for this morning and are expected formally to endorse Barry for reelection.

Some of Barry's labor supporters said that Harris had been "inaccessible" and hostile to labor groups while she held a second Carter cabinet post, that of secretary of Health, Education and Welfare (HEW).

They claim that Harris refused to return calls or answer letters from AFGE officials who in 1980 urged her to intervene in stalled contract negotiations between the Social Security Administration and the AFGE.

AFGE officials said that in the summer of 1980 Harris crossed an informational picket line they set up outside a new federal office building in downtown Baltimore to protest her refusal to get involved in the contract negotiations. Harris crossed the line to attend a dedication ceremony at the building, the AFGE officials said.

Sharon Pratt Dixon, Harris' campaign director, said yesterday that Barry's supporters were exaggerating claims that Harris has been inaccessible to labor while she served in the federal government.

She claimed that Barry has been insensitive to labor throughout most of his term before he began mending fences to improve his reelection chances.

Dixon said that candidates are more interested in the organizational support that might accompany a labor endorsement than the campaign contributions it would generate.

By what seemed a near unanimous voice vote, the union leaders also endorsed City Council member David Clarke (D-Ward 1) in the council chairman's race despite the fact that the labor organization's political education panel had recommended supporting incumbent chairman Arrington Dixon. This was seen by many of the delegates as a reaction to their view that Dixon had backed recent council measures weakening the city's workers compensation and unemployment compensation systems.