Leaders of two major labor unions leaned heavily on President Carter and Congress yesterday to support the union-led drive to overhaul the nation's labor laws, warning of political repercussions if they don't.

But the blunt warnings from United Auto Workers President Douglas Fraser and Jacob Sheinkman, secretary treasurer of the Amalgamated Clothing and Textile Workers Union, drew an immediatedemurrer from the AFL-CIO.

A spokesman for the labor federation, which is negotiating for White House support of the package, said Fraser's and Sheinkman's remarks to a luncheon meeting of the Democratic Socialist Organizing Committee were "unncessarily critical of the White House." He said chances appear good for an agreement soon under which the Carter administration could support labor's package.

The proposal has already been shorn of some of its most controversial features, including repeal of state right-to-work laws, in order to win White HOuse backing and escape a Senate filibuster.

But, even in its modified form, it has encountered stiff resistance from industry groups, which are lobbying to neutralize the White House and pushing their own alternative aimed at weakening union powers and discipline.

As it now stands, the labor proposal calls for procedural changes to speed up union representational elections and contract agreements, injunctive relief to bar unfair labor actions and double back pay for workers who are unfairly discharged in a labor dispute.

Stressing labors's difficulty in organizing the South, Fraser and Sheinkman said that it was all the more important that Carter, a Southerner, spearhead support for the legislation.

Apparently speaking of Congress as well as the White House, Fraser said, "If we can't win this one in the weeks ahead, then we did not win the 1976 election, it's that simple." He said he wanted a verdict before the 1978 congressional elections.

Sheinkman characterized the labor law drive as a human rights effort and said that if Carter was dedicated to human rights at home as well as abroad he would support it. Sheinkman said "some dramatizations of our own on the issue" that would be "embarassing" to some people are possible if the revision package isn't supported.

Asked by a reporter if he was threatening a human rights demonstration in Washington, Sheinkman said "bringing people to Washington for some lobbying" was more likely. "We can tell other countries what to do," said Sheinkman, "but we have to put our own house in order first."