Tape talk in political Washington yesterday included a recorded dinner party at Averell and Pamela Harriman's house, embarrassing portions of which turned up on the front page of The Wall Street Journal. This may be as awful as it gets for a member of Georgetown's most inside circle.

"I am just mortified," said Pamela Harriman. "This has never happened in our house before. We've always trusted people, and people have always trusted us . . . be sorry for me."

The party, held on Sept. 15 in the Harrimans' home, which is decorated with precious art and antiques, was one in a series of gatherings of "Democrats for the '80s." It's a political action committee that raises money to try to rekindle the Democratic Party. The less reverent refer to it as "PamPac."

Every few weeks, Pamela Harriman, the English aristocrat married to the Democratic elder statesman, invites leading Democrats over for wine, dinner and often morose conversation about the future of the nation under the Republicans. Afterward, someone usually asks the guests for contributions.

This is not just any political fund-raiser. Rather, it is a salon where volatile comments are muffled by the privacy that the rich can afford. But on this night, Washington superlawyer Clark Clifford asserted, according to the story by James M. Perry of The Journal, that Ronald Reagan is "an amiable dunce" whose policies will be "a hopeless failure."

Clifford was reported to be fuming at this breach of privacy.

Other luminaries at the party included former Carter campaign chairman Robert Strauss, Sens. Dale Bumpers (D-Ark.) and Alan Cranston (D-Calif.), former senator Frank Church (D-Idaho), former Mideast negotiator Sol Linowitz and Rep. Richard Gephardt (D-Mo.). The discussion centered on Reagan's economic policy. Felix Rohatyn, the New York financier, was the evening's main speaker.

The 38 guests gathered in the Harrimans' library for 20 minutes of talk before dinner. A tape recorder was used, according to several of those present, because Pamela Harriman was recuperating in the hospital from a riding accident and wanted to hear the discussion. A staff member later transcribed the first 20 minutes as well as about 10 minutes of talk after dinner.

According to The Wall Street Journal, Rohatyn concluded that if something isn't done, "society's going to blow up."

This was followed by a lengthy series of accolades. Church said Rohatyn's speech was "a brilliant presentation." Clifford called Rohatyn "one of the outstanding intellects in the country today." Strauss said Clifford was "the wisest man in the room by 2 to 1."

Later, Cranston said there isn't much the Democrats can do "until things deteriorate . . . then our opportunity will come." Shortly thereafter, Linowitz asked: "If the situation is as dire as you all painted it, is it responsible to remain silent?"

"Sol," The Journal reported Bumpers as saying, "that is, boy, that is the legitimate question."

Soon, Pamela Harriman had the written version in her hands. "It was done for me," she said yesterday, enduring a 24-hour virus as well as the riding accident that broke three of her ribs. "Obviously, it will never be done again." Harriman tried to reach some of her guests yesterday to apologize.

Several of them, when reached by a reporter, said they had no idea their conversations were being recorded. "I guess in Washington we have to assume we're always taped everywhere," sighed Gephardt. "There are very few, if any, secret meetings."

Other guests recalled being told of the tape. "I remember Gov. Harriman saying something to that effect," said Church. "He said, 'Let's take the tape of this meeting and we should edit it and then make it available to those who want it.' "

Those who wanted it also included The Wall Street Journal reporter, who won't say where or from whom he got the transcript. And none of the party guests reached by this reporter yesterday was inclined to confess.

But one was mildly irked.

"Some damn fool staffer made copies of that tape and gave it to several people," said Strauss. "I'd fire him for naivete'. And as for me, hell, I wouldn't say anything in a room with more than two people in it."