White House officials have expanded the search for a new secretary of labor beyond Constance Horner, the head of the Office of Personnel Management, who last week was believed to be a virtual shoo-in for the job, according to informed sources.

Strong opposition from the largest federal employe unions apparently was one factor leading the White House to look beyond the director of the civil service to a long list of candidates.

The new list includes Ann Dore McLaughlin, former undersecretary of the interior; Carla Hills, secretary of housing and urban development under President Gerald R. Ford; Betty Southard Murphy, former chairman of the National Labor Relations Board; Patricia Diaz Dennis, a Federal Communications Commission member; Shirley Dennis, director of the Labor Department Women's Bureau; Fred W. Alvarez, commissioner of the Equal Employment Opportunity Commission; Dennis E. Whitfield, undersecretary of labor; Walter C. Wallace, a member of the National Mediation Board, and former House member John Erlenborn (R-Ill.).

Sources familiar with the intricate politics of the labor appointment speculate that Horner remains under consideration with strong support from conservatives.

Horner, Hills and McLaughlin have been interviewed by White House chief of staff Howard H. Baker Jr., sources said.

The White House is eager to nominate a woman to the post because the departure of Transportation Secretary Elizabeth Hanford Dole three weeks ago has left the Cabinet a male preserve.

McLaughlin, a former assistant secretary of the Treasury and public relations executive, served as the No. 2 official in the Interior Department for three years. She is well connected to the conservatives within the administration and is married to John McLaughlin, host of the television show the "McLaughlin Group."

Hills, an anti-trust lawyer and assistant attorney general who served for nearly two years as HUD secretary, was most recently in the news for her strong support of the confirmation of Judge Robert H. Bork as a Supreme Court justice.

Murphy is a labor lawyer who was strongly supported by the Teamsters Union for the labor job in 1981. She was described at the time by Sen. Orrin G. Hatch (R-Utah) as a "consummate labor lawyer, a good manager and a feminist. She is also acceptable to both sides -- labor and business."

Patricia Diaz Dennis is a labor lawyer who has served on the National Labor Relations Board and was recently appointed to the FCC. Shirley Dennis, the head of the Labor Department Women's Bureau for the past two years, served as director of community affairs in the Cabinet of former Pennsylvania governor Richard L. Thornburgh (R). In that job, she was an advocate for low-income citizens and municipalities.

Erlenborn, who has been mentioned for the labor job in the past, said he had not been approached by anyone at the White House about the vacancy. He is regarded as a fiscal conservative and social moderate who has good relations with the labor movement.

Whitfield is an ally of Labor Secretary William E. Brock, who leaves the department Nov. 1 to take over the presidential campaign of Senate Minority Leader Robert J. Dole (R-Kan.).

The AFL-CIO, meeting at its biennial convention in Florida, does not have an official candidate for the job, an official said.Staff writers David Hoffman and Frank Swoboda contributed to this report.