Two-month-old Maria Victoria Walesa was christened today. But her father, Lech, wasn't there.

Poland's military rulers refused to allow the interned leader of the independent Solidarity trade union to attend the politically charged baptism of the child he has never seen. But 7,000 Solidarity supporters showed up and the 45-minute ceremony was relayed to them by loudspeaker from the packed Roman Catholic parish church on the outskirts of Gdansk where the Walesa family worships.

According to accounts from Gdansk, Bishop Lech Kaczmarek, who conducted the service, presented Danuta Walesa with a rosary, which he said was a christening gift for her daughter from Polish-born Pope John Paul II. The bishop prayed for "the child's absent father and for the state authorities in order that they may govern the country justly."

After the service, there were shouts of "Solidarity, Solidarity" and "Bring us Lech" from the crowd. In a telephone interview, Mrs. Walesa said she had hoped to see her husband "right until the very last moment."

What to do with Walesa, who was detained at his home in Gdansk when martial law was declared on the morning of Dec. 13 and later was flown to Warsaw, has posed a major problem for the government. Church representatives tried to convince the government that his temporary release for his daughter's christening would have been seen as a conciliatory gesture toward Solidarity and a step toward national agreement.

The strategy of the authorities, however, seems to be to get Poles to forget about Walesa. Maria Victoria's birth and baptism, which were big news abroad, have gone unmentioned in Poland's tightly controlled news media and television.

Foreign correspondents based in Warsaw were refused permission to travel to Gdansk to attend the service.

Ideally, the martial-law government of Gen. Wojciech Jaruzelski would have liked to extract some kind of statement from Walesa dissociating himself from so-called "Solidarity extremists." But he refused to cooperate.

A nationwide "debate" about the future shape of trade unions in Poland has been launched in the official press without the participation of any of Solidarity's former leaders.

Official spokesmen have denied persistent reports from Solidarity sources of preliminary informal talks between union representatives, including Walesa, and the government. The message is that, even if something is going on behind the scenes, the authorities are strong enough to dictate terms.

The controversy over Maria Victoria's christening has served to illustrate both the government's determination and the continued popular support for Solidarity in its birthplace of Gdansk.

Despite its ostensibly religious nature, the service turned into a show of support for Solidarity and sympathy with the Walesa family, according to accounts from Gdansk. Uniformed police were nowhere to be seen, although plainclothesmen mingled with the crowd, many of whom wore Solidarity badges. Hundreds of people stood on the rooftops of nearby apartment buildings.

A chair stood vacant at the front of the barn-like chapel throughout the ceremony and a large picture of the Solidarity leader hugging Pope John Paul II was pinned to the door.

Maria Victoria is Walesa's seventh child. The sixth, also a girl, was born shortly before the labor unrest flared in August 1980 at a time when Walesa was serving a prison term for trade union activism.

Meanwhile, leading Polish journalists protested the disbanding of their professional association, which was announced Saturday. In a letter signed by the association's president and 21 other prominent journalists, they said a proposed Communist-controlled new union would destroy "any remaining credibility vested in the media" since the military crackdown.

"The authorities are using propaganda to create a crisis. They want to do this with our hands, using the credibility that we were able to gain last year," the journalists wrote.