A senior civil servant at the Defense Ministry was acquitted today of charges that he violated the British Official Secrets Act by sending a member of Parliament embarrassing official documents concerning Britain's conduct during the 1982 Falklands war against Argentina.

The jury's decision that Clive Ponting, 38, had not acted against the interests of the state in revealing details of the May 1982 sinking of the Argentine cruiser General Belgrano was hailed immediately by critics of the secrets act, who charge that its broad wording opens the door to political abuse.

The applicable section of the 1911 act allows the prosecution of any government worker for the unauthorized discussion or passing of any information to any person, even if the information has nothing to do with national security.

Today's decision also has potentially widespread implications for discipline within Britain's career Civil Service. The applicable provision of the act is not often invoked, but is widely used as a deterrent against leaking information. The current case, however, is viewed as perhaps the most controversial because it involves passing of information to a lawmaker rather than to the press or a foreign power.

There were cheers in London's Old Bailey court when the jury of eight men and four women reached its verdict after only three hours of deliberation and despite instructions by the judge that several members of Parliament and other public figures said came close to being an order to convict Ponting.

The leader of a campaign for a freedom of information act in Britain, Des Wilson, called the verdict "the last nail in the coffin of one of the most discreditable pieces of legislation on the statute books."

Ponting was a highly regarded career official whose earlier work had won personal praise from Prime Minister Margaret Thatcher and who had been brought into the office of Defense Secretary Michael Heseltine to prepare a detailed, secret account of what really happened in the Belgrano sinking.

During the course of his work last summer, he had mailed, anonymously and without permission of his superiors, two documents to opposition Labor Party member of Parliament Tam Dalyell. They showed that some of the facts surrounding the torpedoing of the cruiser differed from information given publicly to Parliament two years ago.

According to the documents, the cruiser had been sailing away from the British task force for 11 hours, rather than closing in on it as the government had said. They also showed that the cruiser actually had been spotted a day earlier than the official explanation had stated.

The torpedoing of the cruiser killed 368 Argentine sailors out of a crew of more than 1,000, the highest death toll from a single incident in the 10-week war.

The Ponting case revolves around whether a civil servant can send such material to a person other than one "to whom he is authorized" to communicate or "to whom it is in the interest of the state" for him to communicate.

The judge had told the jury that the interests of the state are the same as the interests of the government in power at the time and that it was clearly not the wish of the government last year that Ponting make this information available.

The judge also pointed out that in testimony, Ponting made it clear that he did not believe Dalyell's charge that the cruiser was not a threat to the British fleet or that the sinking had also torpedoed possible peace talks.

But Ponting had argued that his bosses, Heseltine and armed forces minister John Stanley, had decided to withhold information from Parliament and would send instead "a document that was misleading and deliberately misleading in an attempt to conceal information." Ponting charged that the government was unwilling to admit that it had given Parliament some incorrect information at the time of the sinking. He felt it his duty, he said, not to be a party to that and that members of Parliament had a right to know the facts.

Ponting's lawyer called the verdict "a political decision . . . .It means that the Ministry of Defense was not acting in the public interest. The jury has decided to ignore the obvious direction of the judge. . . . We have not seen anything like it for many years."

David Owen, leader of the opposition Social Democratic Party, said the verdict was "a triumph for common sense. It demonstrates that the interests of the state are not synonymous with the interest of a government . . . and civil servants are not expected . . . to be a party to misleading Parliament."

But Conservative member of Parliament Anthony Beaumont-Dark assailed "a perverse verdict" that "has ended the system of ministers being able to trust civil servants. . . ."