A public clash over how seriously to take Soviet President Leonid Brezhnev's renewed proposal for an East-West moratorium on the deployment of nuclear missiles in Europe has developed between the government of West German Chancellor Helmut Schmidt and leading members of his Social Democratic Party.

The clash present another irritant between the embattled chancellor and some in his party -- including party Chairman Willy Brandt -- and seems bound to contribute to the political muddle threatening to undercut West German support for NATO plans to put new nuclear missiles in Europe.

Brezhnev's suggestion was first put forward in February at the Soviet party congress. It was promptly rejected by NATO governments on the ground that such a freeze would preserve Soviet nuclear superiority in Europe. Nevertheless, Brezhnev floated the idea again last week, using somewhat different language, when he met Brandt in Moscow.

NATO and Bonn government officials have rejected the rephrasing as nothing new.

But since returning to West Germany Thursday, Brandt and Social Democratic Party Deputy Chairman Hans-Juergen Wischnewski, who also was in Moscow, have been insisting in interviews that Brezhnev's new wording represents more than a simple repetition.

They say it contains "new accents" that should be considered seriously by the United States. Beyond that, they have also given new life to the notion that deployment of the NATO missiles beginning in late 1983 well could be prevented by persuading the Soviets to remove some, though not necessarily all, of their SS20 nuclear-tipped missiles aimed at Europe. This is what NATO planners refer to as the "zero option" solution. But the official Western position is that this option depends on Moscow withdrawing all its SS20s, and this is considered highly improbable.

By reviving controversy about a moratorium and the "zero option," Brandt's trip appears to have realized some of the fears of those in the West German government and opposition party who were against the visit, believing it would play into Soviet propaganda designs on Europe and sow more political discord in West Germany.

Grass-roots opposition to the NATO missile decision is strong in West Germany and concentrated, among other places, in the Social Democratic Party. In a strained attempt to keep his party in line, Schmidt has threatened to resign if the party dropped support of the NATO decision, which calls both for missile deployment and U.S.-Soviet negotiations on limiting the number of such missiles.

For Brandt personally, the Moscow trip -- which came at Brezhnev's invitation -- carried considerable significance. It was the former chancellor's first visit to the Soviet Union in six years and punctuated his very recent reemergence as an influential force both in West Germany's unsettled internal political situation and in the country's international relations.

In contrast to Schmidt's firm support of the NATO decision and his tougher stance toward the Soviets, Brandt has sought a more ambiguous approach, which he regards as necessary to integrate the left wing of the Social Democrats with the rest of the party.

Meanwhile, Wischnewski held a press conference yesterday in party headquarters in which he spoke of "important information" contained in Brezhnev's offer to freeze deployment to Soviet SS20s once U.S.-Soviet negotiations on limiting European-based nuclear weapons begin and providing America also does not deploy new missiles.

Comparing closely the text of what Brezhnev said in February with what he told Brandt last week, Wischnewski noted two differences: first, the Soviet chief had dropped his earlier insistence that a freeze also apply to preparations for missile deployment; second, whearas earlier Brezhnev had demanded a formal agreement on a moratorium from the United States, he now was asking simply for a U.S. statement that Washington would go along with a freeze.

Wischnewski also said the Soviets showed "great interest" in the "zero option" solution and had asked Brandt how many SS20 missiles Moscow would have to remove in order to stop the planned NATO deployment of 572 Pershing II and ground-launched cruise missiles. Wischnewski did not disclose Brandt's reply, noting that this number must be left up to U.S. and Soviet negotiators.