The former Polish ambassador to Japan, seated beneath a candle lit by a sympathetic member of Congress to show American solidarity with his people, yesterday called for the United States to end all trade with the Soviet Union and Poland "until our beloved motherland is free."

Zdzislaw Rurarz, who defected from his Tokyo post on Christmas Eve, told a congressional commission that the military authorities in Poland are "a puppet junta" whose strings are pulled from "behind the walls of the Kremlin" and said the United States should adopt a policy toward Moscow and Warsaw of "no trade, no food, no credits."

Rurarz's emotional testimony highlighted a hearing by the commission of Senate and House members charged with monitoring the 1975 Helsinki accords on security and cooperation in Europe.

To symbolize his concern with the plight of the Polish people, one commission member, Rep. Don Ritter (R-Pa.), lit a yellow candle in a 100-year-old candlestick that he said had been brought from Warsaw by a woman fleeing an earlier siege of oppression in Poland.

In the ensuing hours, the candle burned to the holder's socket and was replaced with a fresh one as the hearing, chaired by Sen. Robert J. Dole (R-Kan.), heard Rurarz and a parade of other witnesses denounce the Soviet Union and Poland's military rulers headed by Gen. Wojciech Jaruzelski.

Max Kampelman, chief U.S. delegate to the conference in Madrid charged with continuing the progress of the Helsinki accords, called the Polish crackdown a "blatant violation" of the accords' human rights provisions and warned that it could mean the death knell for the agreement, which was designed to provide a basis for peaceful relations between Western and Eastern Europe.

While Kampelman cautioned against the United States declaring the Helsinki agreement void, a representative of the AFL-CIO said on behalf of the labor federation:

"We believe the time has come for the U.S. government to declare that the Soviet Union and its Warsaw Pact allies have unilaterally abrogated the Helsinki agreement."

Tom Kahn, an assistant to AFL-CIO President Lane Kirkland, proposed several sanctions, including calling in Polish debts to the United States, refusing to extend more credits to the Soviet bloc, reinstituting the grain embargo against the Soviet Union, stopping participation by U.S. firms in construction of a gas pipeline across Siberia, severely restricting Soviet access to U.S. technology and denying Soviet vessels easy access to U.S. ports.

Of all the witnesses, the biggest impression was made by Rurarz, whose defection came shortly after the Polish ambassador to Washington, Romuald Spasowski, was granted asylum here.

In response to a personal request from Spasowski, President Reagan, during his televised Christmas message last week, said he would place a lighted candle in the White House window and urged other Americans to do the same.

At yesterday's hearing, Rurarz acknowledged Ritter's gesture by recalling how moved he had been when he and his wife and daughter arrived at Dulles airport on Christmas Eve and saw candles displayed in the windows of many homes as they were driven into Washington.

He spoke in halting English that frequently made his words difficult to understand. But there was no mistaking the emotion in his voice as he denounced Jaruzelski as "a traitor . . . who had played the most dirty game in our history," called the imposition of martial law "a declaration of war by the government against the nation," and charged:

"The real maker of the Polish drama is behind the Kremlin walls."

Rurarz asserted that from the time the Polish reform movement began stirring 16 months ago, the Soviet Union "was pressuring the Polish government to roll back the situation" and that the Polish authorities, from the outset, engaged in "delaying tactics" to buy time while preparing for repression of the independent Solidarity labor union.

He said he had no doubt about the government's intentions after he received a cable in Tokyo last March 27 advising him to be prepared for declaration of a state of emergency against Solidarity, then threatening a general strike.

In November, Rurarz continued, he learned that the crackdown was likely to come in December when severe winter weather would make resistance more difficult.

Of Jaruzelski and the other leaders of the military takeover, Rurarz declared, "I hope they will not escape the punishing hand of justice," and he appealed to the commission: "Please do not give a single penny to the perfidious Polish junta."

Kampelman, noting that the Madrid follow-up conference on the Helsinki accords is in recess until Feb. 9, said the United States cannot go back on a "business-as-usual basis" and must be able to challenge the Soviets and their allies at the next sessions with "something more than rhetoric."

But he added that a renunciation of the Helsinki accords would almost certainly be resisted by European allies who believe the agreements are still a potentially useful vehicle for diplomacy.

John D. Scanlan, deputy assistant secretary of state for European affairs, testified that the crackdown "has plunged Poland into the darkness of an arbitrary abridgement of human and civil rights worse than anything known in Poland since the 1950s."

Scanlan said the Polish government has admitted arresting at least 5,000 people and added that there are grounds for believing the number of detainees is much higher.