As never before since the Polish crisis eroupted last summer the Kremlin is signaling that the erosion of the Communist Party's power over Poland must cease if outside intervention is to be avoided.

Soviet propaganda in the last 10 days has denounced leaders of the Solidarity independent trade unions as antisocialist thugs and taken bitter aim at the dissident Committe for Social Self-Defense (known as KOR). The attack has broadened from thrusts at "branch" unions and "rightwing elements" within Solidarity's leadership to include the entire leadership of the independent labor movement.Using the official Tass news agency as its principal outlet, Moscow now says the Polish United Workers' (Communist) Party faces a frontal assault on its political power.

That allegation seems especially serious to foreign diplomats, and Soviet sources as well, who from the beginning of the turnmoil in Poland have said the Kremlin would not intervene so long as it was confident of both the political allegiance of Warsaw to Moscow and the Polish party's control.

There is no doubt here that the Kremlin remains assured of Warsaw's allegiance. With the choice of Defense Minister Gen. Wojciech Jaruzelski as the country's new premier yesterday and a tough speech from party leader Stanislaw Kania at an emergency meeting of the Central Committee today, the Communists show every sign of trying to harden their adherence to Moscow and the Warsaw Pact.

However, while Kania clearly senses that Moscow's patience with his inability to impose firm limits on the labor unions' activism is running out the question of control remains unclear. On that crucial issue, it is suggested by some here, the Soviets may be insisting behind the scenes that Warsaw must take direct steps to cut back the spread of political activism.

In the Soviet context of complete party control of every aspect of economic and political life, the Polish Supreme Court's compromise ruling today that the country's farmers can form associations but not unions only represents further erosion of party supremacy.

The decision seems likey to give Polish peasants new powers to choose for themselves what crops to plant independent of state plans. It thus seems to be a new barrier to the notion of farm collectivization which Moscow dogmatists believe is the only correct path to ideological purity and control, despite the Soviet Union's severe agricultural problems and the quiet but successful deviations elsewhere in the bloc, as in Hungary.

Significantly, however, Moscow has not criticzed the courts either in today's decision or the earlier decision giving the trade union movement new freedoms. Instead, it has concentrated its attacks on activists, portraying them as disruptive "outsiders" within the social community, where party and people are supposed to display unanimity of views.

The denunciations of KOR, echoed by media in East Germany and Czechoslovakia, lead some analysts here to speculate that the Soviets may be trying to establish grounds for behind-the-scenes demands that the dissident movement be supressed. Althogh past police moves against KOR have only added to Warsaw's troubles, Moscow may see a campaign against the dissidents as one of the few ways the party can show its toughness after endless concessions to the independent trade unionists.

It is certain that the Kremlin was happy to see the ouster of Premier Jozef Pinkowski, and most observers here say Moscow, if not demanding his resignation, certainly informed beforehand, and probably exercised veto power over the choice of a successor.