The Democratic liberal establishment, disturbed by the conservative direction of the Carter administration, has sent a clear warning signal to the White House - proceed as you are at your political peril.

That's the message being passed privately and publicly from leaders of Americans for Democratic Action, meeting here this weekend to celebrate ADA's 30th anniversary.

Yesterday, ADA members heard a stinging attack on the Carter administration by Sen. George McGovern, the Democratic presidential nominee of 1972 and now ADA's president. The day before, a delegation of 15 ADA national leaders met privately with Vice President Mondale in the Caibiet Room at the White House. They told him bluntly they felt President Carter wasn't keeping his campaign promises in a number of areas.

One of the participants in that meeting described what he said was a dramatic moment when one of the ADA members toold Mondale directly:

"I decided to give money, to work my head off for candidate Carter when I received a letter from him saying. 'I promise you that if I'm elected President of the United States, there will no annual increases in the defense budget and we will do the social programming we promised.'

"I went out and raised money for him and gave money myself and worked very hard for him. "I don't see that pledge being kept."

McGovern's speech, while not as directly critical of Carter personally, nevertheless represented perhaps the sharpest public attack on his leadership to date from a liberal Democrat.

The South Dakota senator began by remining ADA members that only a year ago they had campaigned for the Democratic party and for the principles it pledged. Now, political victory notwithstanding, they find themselves still struggling for those principles.

"The effort may be lonely for a while," McGovern said. "A strange silence has descended on our political life. We all seem mesmerixed by image, taken by symbol. We seem to count the ratings of polls far more than the content of policy. Only the first hundred days of this new administration have passed, but these early days may be setting the shape of the next thousand. I believe it is imperative to talk plainly of the concerns which many have, but most are reluctant to speak."

He continued, in similar vein, with barbed allusions to the Carter presidential style: "The advocates of change must not be content with labels, symbols and small consolations. We must not trade full employment for a town meeting. Those who talked back to John Kennedy should not be afraid to speak up to Jimmy Carter."

Other McGovern passages added up to a scathing indictment of administration policies.

"In reviewing economic policy this spring," he said, "It sometimes seems difficult to remember who won last fall."

he spoke of "business appeasement at full tide" threatening to sweep away basic Democratic commitments in such areas as health care, welfare reform, tax cuts for individuals, promised reductions in the defense budget. He deplored administration attempts to "balance the federal budget on the backs of the poor, the hungry and the jobless."

Last night, U.N. Ambassador Andrew Young gave a gentle response to McGovern for the Carter administration. Young said that fiscal responsibility "need not be anathema to liberals." The former civil rights leader said that blacks in the South had learned that strong social programs for the poor were not possible without the money to pay for them. Young stepped around the ADA's criticism of Carter by saying. "ADA is eternally discontent. It is its role to be critical."

McGovern's most critical remarks came at the end:

"We wants to be able to applaud the President's record as strongly as we approved the platform on which he ran. But we will not be a cheering section for tinkling symbols that may signify nothing. We will not agree to substitute cold technocracy for compassionate values. We will never be, as one Carter adviser wrote of some other Democrats, among "the easiest to dominate.' We do not happen to have what that adviser called a 'willingness to accept any status quo that provides . . . power and patronage.' Rather we seek to call our party to a high standard."

The unnamed Carter adiser was the President's pollster Patrick Cadell, whose confidential memorandum on Carter initial administration strategy was leaked to the press several days ago. Caddell's advice to the incoming President emphasized attempting to appeal to conservatives.

Caddell, ironically, came to political prominence as George McGovern's pollster in the 1972 presidential campaign.

But the liberal disquiet with the Carter administration now being publicly expressed goes beyond personal pique. For weeks there have been rumblings of discontent from liberal Democrats in Congress. This last week opposition began to harden after Carter told congressional leaders on successive days that a primary concern was to balance the budget by 1981, even if that mean promised programs, like welfare, would have to be put off.

ADA's 30th anniversary meeting happened to coincide with recent events, and growing opposition.

At the meeting with Mondale, attended by such ADA leaders as McGovern, Joseph L. Rauh, ADA's vice president, the Vice President was told that one of the elements of great leadership was a willingness to take risks.

"We set forth our view that there's no risk in talking about a balanced budgets in fiscal 1981 if the result of that was a breaking of all the pledges in the Democratic Party platform." said Shull, "a breaking of candidate Carter's pledges. In the final analysis he campaigned on those issues. If that's what's going to mean, then I think that the year 1980 is going to be a very different year for new candidate Carter."

Mondale, accompanied by Stuart Eizenstat, a key Carter domestic counselor, reportedly replied that the administration had done more than the group seemed to recongnize, and that more time was needed to get programs in place.

The meeting was without rancor. Mondale probably has no stronger supporters than those in ADA; he was, virtually, their unanimous choice for President. But the message given the administration he now represents was clearly stated.

As Shull said later, if Carter's presidential action doesn't match his campaign rhetorie, he will face strong opposition.

Shull has been in all of ADA's major battles going back to the Democratic convention floor fight over civil rights in 1948. He participated in the Joe McCarthy struggles, the Vietnam trauma, the Watergate-impeachment denouncement. Jimmy Carter, in some ways, represents a more difficult questions - the first Democratic President in eight years, who campaigned on many populist themes, and who has skillfully built a popular political base nationally. Yet he seems to be, to an ADA leader like Shull, a "fiscal conservative."

"I suppose what we have to be able to work out," Shull said, "is to challenge him skillfully where we think he's wrong, support him where we thing he's right and persuade him that way to build public pressure."

But if that doesn't happen. Carter has now been put on public notice to expect harsher handling from the liberals. As Shull says:

?Just as with Lyndon Johnson, if Carter follows policies which in the judgment of the liberal movement are not in the best interests of the country, then that liberal movement, with ADA in the forefront, will go into the opposition. And I think there are some lessons in this. I think Lyndon Johnson didn't understand that and failed to recognize the fact that you couldn't disregard the liberal movement."