The Dutch Reformed Mission Church today exonerated Allan Boesak, a prominent Colored church leader and apartheid opponent, after the minister testified that his extramarital affair with a young church worker had been a "unique" and innocent one.

After allegations against Boesak were published in the Johannesburg Star last month, based on information gathered by security police, Boesak admitted a "relationship," although he did not specify its nature.

The church provisionally suspended the pastor while it investigated what it would regard as a serious moral lapse for a Calvinist minister. But the principal issue quickly became whether the government was using a prominent opponent's private life to discredit his views.

While the church presbytery delivered its verdict today reinstating Boesak, a media council investigating the newspaper's role in the matter heard a senior security police officer admit that his arm of the security apparatus sometimes uses "disinformation" and other methods to discredit what they regard as subversive organizations.

The officer, Brig. Johan Van der Merwe, who is second in command of the security police, denied trying to discredit Boesak, but said he could see nothing immoral in spreading false information about "subversive" organizations, such as the South African Council of Churches, to which Boesak belongs, "so long as it does not harm the morals of the community we serve."

Boesak expressed his relief after the verdict was announced early this morning. The church gave no details of its deliberations and conclusions.

"This Sunday I will be back in the pulpit," Boesak said. "One of the most gratifying things to come out of the whole affair is that I now have more support than ever. I will continue to fight the government at every level."

There have been a number of instances in which the government has used a political opponent's private life to try to discredit his views.

In Boesak's case, the security police admitted at the media council hearing that they were "monitoring" his activities because they regarded them as "potentially subversive."

According to Van der Merwe, the security police discovered that he was having a love affair with a young white staff member at the church council, Diana Scott.

Van der Merwe has said in his testimony to the media council that the security police ignored this because it was a "private matter" in which they were not interested. But two reporters of the Johannesburg Star, South Africa's biggest daily and one of its most reputable newspapers, have testified that the security police passed information about the affair -- including a tape recording of a "bedroom scene" -- to their editor.

The Star published the report about the affair, but at the same time it accused the security police of engaging in a "dirty tricks" campaign to discredit the clergyman.

The security police lodged a complaint against The Star's "dirty tricks" report with the media council, a body set up recently by the newspaper industry under government pressure to hear allegations of unfair reporting.

Boesak's opposition to apartheid from within the Colored (mixed-race) branch of the racially segregated Dutch Reformed Mission Church, to which most of the progovernment white Afrikaners belong, has made him a thorn in the administration's side.

Two years ago Boesak led a campaign to have apartheid, the policy of racial segregation, declared a heresy by the World Alliance of Reformed Churches, which then suspended two white branches of the South African church for supporting it. To the further mortification of white Afrikaners, Boesak wound up being elected president of the world alliance.

Soon after this he played a key role in establishing an alliance of antiapartheid organizations called the United Democratic Front, which rapidly has developed into the biggest and most effective black opposition movement since the main African nationalist parties were outlawed 25 years ago.

The front has been the major influence in organizing black protests that have led to the wave of racial unrest in which more than 200 blacks have been killed since September.

Because of the international status of his church position , the government has seemed reluctant to act against him, as it has against other front leaders, 16 of whom are now in prison awaiting trial on charges of high treason.