President Carter's national security affairs adviser, Zbigniew Brzezinski, yesterday criticized West Germany's failure to meet its pledged defense spending target as "disappointing . . . disturbing . . . unfortunate."

In a breakfast meeting with reporters, Brzezinski went on to say that the German action, announced Wednesday in Bonn, could have the effect of "weakening the cumulative resolve of the alliance" at a time of tension between East and West.

As announced by the West German government, its new defense budget will include a 2.2 percent increase in real terms, short of the 3 percent target pledged by all members of the Atlantic alliance. But Brzezinski said a more correct calculation was that the German military budget will rise only a little more than 1 percent when properly adjusted for inflation.

Regarding the western reaction to a possible Soviet invasion of Poland, Brzezinski acknowledged that some western European governments, including that in Bonn, have important economic stakes in East-West relations and therefore are reluctant to commit themselves to strong retaliatory measures in advance.

Nevertheless, he said, those governments realize that a Soviet invasion would bring "a very strong public reaction" in Europe that would make continuing commercial relations with the Soviet Union "well nigh impossible." Brzezinski also predicted a strong trade-union reaction worldwide in the event of an invasion.

While not officially downgrading the chances for Soviet military intervention, the tone of Brzezinski's comments was notably less one of alarm and imminent danger than were pronouncements by high officials a few days ago.

The United States sees "no change in the objective circumstances" surrounding Poland, he said. Moreover, he appealed to the Soviets to change their deployments, saying "it would be desirable and contribute to a lessening of tension" if Soviet verbal assurances of nonintervention were accompanied by "disengagement of [Soviet] forces" in central Europe.

At the same time, Brzezinski commented favorably on Tuesday's memorial observance in Gdansk, Poland, which arrayed together leaders of the Communist Party, the Roman Catholic Church and labor unions, the three main internal forces in that country. Most Poles found this reassuring, he said.

More so than in previous U.S. pronouncements, Brzezinski spoke of the positive effect of a peaceful resolution of the tensions within Poland. If the situation there evolves peacefully, he said, "it should greatly improve the international climate."