On the eve of Secretary of State George P. Shultz's visit here for talks with Prime Minister Margaret Thatcher and other senior officials, British government support for American nuclear policy came under severe attack in Parliament by opposition parties.

Denis Healey, deputy leader of the Labor Party, reflecting a substantial upsurge in Britain of public and political criticism of U.S. positions, said he was "appalled by the callous indifference Thatcher has shown to the idea of arms control."

For the government, Foreign Minister Francis Pym today stressed its basic support for American nuclear strategy, but he acknowledged in an interview that if no advance is made on the U.S. "zero option"--a demand for the Soviet Union to dismantle all its medium-range missiles in return for cancellation of American deployment of cruise and Pershing II missiles scheduled to begin next year--the allies would have to "consider alternatives."

"We may have to contemplate an agreement," he said, "that, while not zero, would be very much lower than the level now in existence or in mind." The time for such a bargain, he said, had not yet arrived despite the Soviets' recently expressed willingness to offer lesser cuts.

In the interview and later in Parliament, in a major defense of the government's stand, Pym underscored that unless the allies "remain resolute" about the scheduled deployment, "there is no incentive for the Russians to talk at all."

Pym also ruled out "in the present circumstances" the possibility that British nuclear nuclear weapons could be included as part of an arms-reduction bargain with the Soviets, which the Kremlin has also proposed.

The British arsenal consists of submarine-launched missiles, he argued today, not the land-based weapons at issue in the Geneva Intermediate Nuclear Force talks.

His remarks underlined the problem for the Thatcher government posed by the U.S. deployment plans unless progress emerges in arms talks with the Soviets.

After reaching a peak of public opposition in the fall of 1981 with mass marches and protests, the antinuclear movement in Britain had until recently receded into the background of political activity. The Labor Party's overwhelming vote at its annual conference this fall for a policy of unilateral nuclear disarmament showed the continuing strong sentiment against any nuclear weapons, while the pace of public protest specifically against the cruise is again picking up.

Over the weekend, 30,000 women ringed the nine-mile perimeter of the planned cruise base at Greenham Common in the Berkshire countryside where 96 missiles are to be deployed next year. The next day, a thousand women staged a day-long blockade of the base. The protesters vowed to keep up their activities until the deployment is stopped.

One issue of concern to critics is British control of the weapons. Pressed to pledge that the British Cabinet would be able to veto use of missiles fired from this country, Pym said, "I can't give that assurance."

Opposition politicians also pounced on a plan described in a report from Washington last week by The Guardian for development of an "alternative" U.S. European command headquarters to the one at Stuttgart, West Germany, for use in wartime. Thatcher reaffirmed that plan today, saying an alternative headquarters could be set up at the High Wycombe Air Force Base, northwest of London.

On another subject, the possibility of lifting sanctions against Poland instituted after martial law was imposed a year ago, Pym said he was doubtful that recent moves toward easing the martial law regimen by the government in Warsaw could justify any lifting of the curbs.