In a show of renewed opposition, 14 leaders of the banned Solidarity trade union today protested the imprisonment of seven union colleagues and demanded "a stop to all kinds of repression" by the government.

The appeal was particularly significant for, in addition to ex-union chief Lech Walesa, it included the signatures of former top-ranking union activists from all over Poland, indicating that contacts between them are being maintained after their release from internment and the suspension of martial law last month.

Meanwhile, the government today gave its first low-key public answer to Walesa's recent bid to return to his old electrician's job at Gdansk's Lenin Shipyard, scene of Solidarity's birth in August 1980. In an interview in a Gdansk newspaper, a regional administrator said Walesa was acting like "a whimsical film star," but he suggested the former union leader could go back if he would first see his way through a bit of official red tape.

In their strongly worded condemnation of the arrest of seven prominent Solidarity leaders who were not released last month when the last of those interned under martial law were freed, Walesa and 13 cosigners said the government had no grounds for legal action.

The seven are reported under investigation on charges of conspiring to overthrow the government, but today's statement said the men had done nothing more than get involved in the activities of a trade union that was created from worker-government agreements and that functioned according to Polish law and international conventions.

"Charging them means charging the union, and their trial would be the union's trial," said the declaration, which was distributed to western correspondents. "Imprisoning the seven internees violates the basic principles of justice and deprives of value all the promises and announcements by the authorities."

The statement also objected to the continuing campaign of arrests by police as they uncover hideaways and printing machines used by the political underground in the past year, and to "secret forms of internment"--an apparent reference to what underground publications say is the practice of calling up former Solidarity activists from the military reserve for work in special labor battalions.

A government spokesman has said that 1,500 remain in prison for political crimes, about 1,000 of them already convicted and serving sentences ranging up to 10 years.

Seeking public support, the ex-Solidarity leaders put forward three demands: the release of all those arrested under martial law; protection of civil rights and a stop to repression, and the guarantee of union rights for working people.

Joining Walesa in signing the appeal were Bronislaw Geremek, 50, a medieval historian who was a personal adviser to the Solidarity chairman; Tadeusz Mazowiecki, 55, a Catholic intellectual who edited the weekly Solidarity newspaper; Janusz Onyszkiewicz, 45, the union's former press spokesman, and leading unionists from Lublin, Elblag, Wroclaw, Radom, Bygdoszcz, Gdansk and Warsaw.

As for Walesa's efforts to retrieve his old shipyard job, Poland's Communist authorities seemed inclined to play down a confrontation that Walesa last week was playing up. In full view of western television, the ex-Solidarity chief had asked at the shipyard gates to be returned to work. He was told to visit the Gdansk district administrator for certification that he was no longer a union leader and to clear up the matter of Solidarity's tangled finances.

Alleging harassment, Walesa refused, saying of the administrator's office: "For me, it does not exist." But the man Walesa had been instructed to see--Boleslaw Napieraj, who is in charge of the property and paychecks of Solidarity's former national commission members--proved today he does exist. Speaking to a Gdansk newspaper, he needled Walesa for refusing to settle "routine formalities."

"I have to clear the formalities related to the resumption by Walesa of a regular job," Napieraj said. "Meanwhile, he obstructs it and I don't know why." The Gdansk official also said he had no intention of creating problems for Walesa in going back to work at the shipyard.

While this standoff continued, Poland's senior Communist officials gathered in Warsaw for an extraordinary conference on a deeper national dilemma: how to feed an increasingly hungry country. For the first time in Poland's post-World War II history, a joint session has been convened of the Central Committees of the ruling Communist Party and the Peasants' Party.

The two-day meeting is not expected to produce a new program for agriculture. But against the background of lagging investment in food-producing equipment, a severe grain and beef shortage and nearly 4 million disgruntled farmers, the authorities intend to show a renewed commitment to farming while lowering agricultural production goals for the next few years.