battered by declining union membership, bargaining failures and the resounding defeat last fall of their endorsed presidential candidate -- are meeting at a Florida resort hotel this week for what has become their annual winter soul-searching and political rebuilding effort.

The 35 international union presidents and federation officials have assembled for the first time since the defeat of Democrat Walter F. Mondale, who received the AFL-CIO's unprecedented pre-primary endorsement and a record amount of labor money. The agenda, in addition to economic issues, includes the direction of the Democratic Party and the labor movement.

The pressure for change is intense because of labor's deteriorating image, its portrayal as a special-interest group within the Democratic Party and its potential loss of clout because of its hostile relationship with the administration, according to public opinion polls, labor experts and union officials.

"There is a lot of new thinking going on about what we can do differently and do better, on political education and other issues," said AFL-CIO information chief Murray Seeger.

But resistance to change is entrenched among old-line labor leaders. While forces within the Democratic Party suggest the need for a more conservative thrust to attract mainstream America, labor remains strongly opposed to such a fundamental shift, judging from interviews with political directors of some of the nation's largest unions.

Nor is labor prepared to lower its profile within the party or abandon its strategy of a pre-primary presidential endorsement, assuming that a labor-approved candidate emerges in the next few years.

"A lot of people say we've got to change and become more like Republicans," AFL-CIO President Lane Kirkland has said, but he and other key labor figures reject such notions, according to Dick Murphy, political director of the Service Employees International Union. Murphy said the "defection" of white male and Southern voters to the Republican Party, although of deep concern to labor, is not enough to prompt a basic philosophical shift.

Kirkland today is expected to deliver the AFL-CIO's critique of President Reagan's proposed budget. Later this week the executive council is to receive a long-awaited report from its Committee on the Future, recommending new thrusts in organizing, public relations, use of media and political strategy.

Labor's costly 12-month campaign for Mondale has been widely criticized as a futile effort at king-making that ultimately backfired and hurt Democrats. Sen. Gary Hart (D-Colo.), formerly close to the AFL-CIO, sharply attacked Mondale as a tool of labor, a label that dogged Mondale and unions throughout the campaign.

But within the 96 unions that make up the federation, belief is expressed that, although labor's candidate may have been whipped, the unions, at least, did their part. They raised about $40 million for Democrats in 1983-84, delivered 55 to 60 percent of the labor vote to Mondale, helped swing key Senate races and, perhaps most important, stayed united.

Mondale is to visit the council during its week-long meeting in Bal Harbour, Fla., to thank the 13 million-member federation for its political support. Senate Majority Leader Robert J. Dole (R-Kan.) and Senate Finance Committee Chairman Bob Packwood (R-Ore.) also have been invited to speak.

After Reagan's victory, "there was great disappointment, but there are a number of us who thought we did rather well under the circumstances," said William Hoylater, political director of the International Association of Machinists. "We picked up a couple of Democratic friends in the Senate, we lost only a small number in the House . . . . It could have been a lot worse."

Most labor leaders see Reagan's 49-state landslide as a victory of a popular incumbent riding the crest of an economic recovery based on deficit spending, rather than a repudiation of Democrats.

"We go over what happened a million times, and the conclusion is that there was absolutely no Democrat, alive or dead, who could have defeated a very popular incumbent president," said Loretta Bowen, political director of the Communications Workers of America. "I don't see what radical changes should be made in the Democratic Party."

Mondale's political coordinator, Paul Jensen, said there is "no question" that the labor vote saved Mondale from a defeat by Hart. He added, "The next Democratic nominee for president will be the one who can get the assets of labor -- without inheriting the potential liability of that association with so-called special interest."

Paul G. Kirk Jr., the newly elected Democratic National Committee chairman who won the post with strong AFL-CIO backing, said at a recent news conference that "the trade union movement has made a tremendous contribution to our society and our party," adding that the party's failure was in broadening its base among other groups. "We have to have other constituencies . That was the lesson of 1984."

A key lesson within labor is the need to emphasize grass-roots political efforts, Seeger said, pointing to AFL-CIO polling data showing that Mondale scored roughly 25 percent higher among union members contacted by union colleagues.