Barbara Honegger, the departed Justice Department consultant mocked by one Reagan administration official as a "low-level munchkin," was embraced yesterday by leaders of women's organizations as "nothing less than Reagan's smoking gun on women's issues."

Flanked by leaders of the National Organization for Women and the National Women's Political Caucus, Honegger told a packed news conference: "The White House knows they cannot discredit the content of what I said, so now they have gone after me." She held up a color photograph of herself and Reagan, saying: "This is the munchkin with the Wizard of Oz."

Meanwhile, in an interview with the Gannett News Service, Reagan defended his policies. He said he believes laws differentiating between the sexes benefit women more than the Equal Rights Amendment would.

"I'm surprised that more of them women have not looked at how much mischief could be done" if the ERA were adopted, Reagan told reporter Ann Devroy. "Labor regulations . . . are definitely there for the benefit of women. I could see some troublemaking men, mischief-makers just saying, 'Well look, I don't have to do that' " if the ERA passed.

Honegger, who headed a Justice Department project to identify federal laws discriminating against women, resigned Monday after The Washington Post's publication Sunday of an opinion article she wrote calling Reagan's policies on women "a sham." The article concluded: " F rankly, my dear, I don't think Ronald Reagan gives a damn" about women's rights.

"The president has at no time supported any concerted effort to win equality for women. The proof is here from an inside source," NOW president Judy Goldsmith declared, standing beside Honegger before 12 television cameras and a mob of reporters.

In place of the ERA, Reagan proposed a project to root out federal and state laws discriminating against women. But Honegger, a former White House aide who helped draft Reagan's "ERA alternative," said the White House repeatedly ignored her compilations of discriminatory laws.

Reagan's approach "was a lousy alternative to the ERA , but it could have worked" if Reagan and his aides had carried through with it, Honegger said at the news conference at NOW headquarters.

Honegger announced that she will attend today's meeting of Republican women in San Diego, which the president is to address and feminists have announced plans to picket. She said she will deliver to Maureen Reagan, the president's daughter and newly appointed National Republican Committee liaison on women's issues, a letter calling on Reagan to renounce his previous stands and endorse the ERA.

At the news conference, Honegger was tearful and appeared spent after three days of media attention. She explained that she had had no previous experience as a public figure.

Honegger spent the hour after the news conference closeted with two public-relations consultants who said they were volunteering their time, and with Kathy Wilson, who chairs the National Women's Political Caucus. She then went home, sending word that she was "totally exhausted."

Honegger has captured so much attention that several feminist leaders said they feared that the substance of issues would be lost in the uproar.

The White House has not attacked the accuracy of Honegger's criticism but has attempted to discredit her. White House spokesman Larry Speakes said this week that she "was the Easter Bunny at the White House Easter Egg Roll." Honegger rebutted that yesterday, pointing out that Ursula Meese, wife of White House counselor Edwin Meese III, dressed as a bunny there.

Other administration officials directed reporters to Honegger's interest in parapsychology.

In addition, The Washington Times reported this week, she appeared last year at the National Spiritual Science Center and gave a speech entitled, "The Shimmering Door: Key to Lucid Waking Reality."

"I hope the very serious issues and substance do not get buried in all of this discussion," said Mary Berry, a member of the U.S. Civil Rights Commission and a critic of Reagan's policies on women's rights.

"We know that women are severely at risk," she said, citing administration resistance to affirmative action and its recent effort to narrow the scope of laws banning discrimination by educational institutions.

Berry shared the podium yesterday with Honegger, Goldsmith and Wilson. But virtually all of the media attention focused on Honegger, who at 5-foot-1 was barely visible behind the lectern when she stepped forward to speak.

An official of NOW, which sponsored the news conference, brought out a stool for Honegger, but she demurred: "A pedestal? Oh, no. I'm not going to stand on that thing. It's the wrong symbol." Seconds later, she gave in.

With her metal-rimmed glasses and straight, shoulder-length hair, Honegger appeared bookish and retiring. Her voice cracked several times, particularly when asked whether she expects that Maureen Reagan will persuade the president to change his policies.

"Maureen Reagan has already sold her soul," Honegger said. Asserting that the president's daughter belittled her in a television interview yesterday after praising her courage days earlier, she said, "What has brought about the 180-degree shift in this woman? I'm terribly sorry and afraid for Maureen."

Attempting to refute White House criticism, Honegger distributed a written statement explaining that she had appeared twice at Reagan-related functions in a rabbit costume but not at one of the annual Easter Egg rolls on the White House lawn.

She said she wore the costume for a photograph of the Reagan staff sent to White House press secretary Brady, wounded in the Reagan assassination attempt, in hopes it would cheer him.

In reply to other charges that she was a low-level functionary, Honegger held aloft photographs of her with Reagan and of her with Reagan and former White House policy development adviser Martin Anderson. Anderson, Honegger's supervisor at Stanford University's Hoover Institution and later at the White House, had written on the picture: "To Barbara, the conscience of the Office of Policy Development."

A NOW official who asked not to be identified said she viewed the Honegger story as a case study of women's problems with the administration.

"She really believed in the president and was working for him. She found he was betraying women, and now the administration is betraying her, trying to ridicule her and her capabilities," the official said. "I'm just sorry she had to find out the hard way what we already knew."