Journalists enjoy the power to make or break lives with extraordinary ease. A simple assertion in a story whether true or not has the potential to ruin a career, reputation or business.

On the other hand, a lazy journalist who relies on one source for a story can build up that person's status without ever intending too. Sometimes there is an extreme version of the effect of writing in the mass media, such as when a Nigerian columnist wrote a throwaway line last year about the prophet and Miss World contestants that sparked a riot and left 200 people dead.

More often it is a small thing, such as when the presence of a television camera and the short-term celebrity status it can bestow on ordinary people raises their hopes that it will lift them out of their sad lives. Very occasionally, it does. Usually it leaves the subjects disappointed that, having exposed themselves to the world, they got little in return.

Every journalist has had the experience of winning the confidence of someone who is in some way a victim and who believes despite every assurance to the contrary that the attention of a news reporter will help them. Every journalist has had to leave such people behind to move on to the next story and win the confidence of someone else with a story to tell. Even with the best of intentions reporters can leave hurt in their paths.

Yet we bestow on them such power, and protect them against those who would limit it, because they can use it to scrutinise the rich and powerful, expose the plight of the weak and poor and serve the public good.

On balance, journalism does this. But not always, especially when newspapers are under pressure to reverse a decline in audience or they throw out the window self-imposed ethical rules that are meant to limit the damage they may do.

These thoughts came to mind when I spotted the City Press headline on Sunday, asking if the national director of public prosecutions, Bulelani Ngcuka, had perhaps been an apartheid spy. It was an astounding story. They published little evidence to justify the allegation, except the word of some of Ngcuka's bitter political enemies.

It was self-evidently a crude attempt to discredit Ngcuka in his battle with Deputy President Jacob Zuma and former minister Mac Maharaj.

City Press ran an editorial alongside the story, which seemed to do little more than show that they knew that they were sticking their necks out legally and ethically in doing what other newspapers had declined to do.

The information had been around most newsrooms for weeks, but others had been constrained to report only that there were attempts afoot to discredit Ngcuka through leaks and innuendos.

There is a history of such stories in SA. The security police often used such leaks to cast doubt on apartheid activists, just as they would detain their real spies to give them credibility in the resistance movement.

One of the lowest points in South African journalism was in the 1980s, when The Star ran an accusation that the killer of anti-apartheid activist and intellectual Ruth First was her own husband, Communist Party leader Joe Slovo. Their sole source, it turned out later, was the security policeman who sent the bomb that killed her, Craig Williamson.

Many years later, The Star ran a frontpage retraction and apology.

In the Ngcuka case, the ironies are huge. The very people who have been attacking the media for making unsubstantiated allegations and using dubious sources are using the same tactics when it suits them and are showing great skill in it.

It seemed to me that City Press missed the real story: Zuma, as former head of African National Congress (ANC) intelligence, holds all sorts of dirt on ANC leaders, and is prepared to use it when it suits his personal ambitions.

One recalls that it was Zuma who, after finding out that the late Peter Mokaba had been compromised by the security police during a spell in detention, then protected the youth league leader.

I suspect that Zuma rather liked having a senior ANC person beholden to him, and one can't help now but think back on how eagerly Mokaba embraced Thabo Mbeki for president. And how silent Mbeki is on the Zuma issue.

One recalls that it is the ANC that has resisted the release of names of former apartheid spies, even when they are verifiable. It is, I suspect, more useful to keep and use such information.

The usual newspaper defence for running such stories is that they are telling the truth, and the truth is always in the public interest. In this case, now that Ngcuka has sued, we will see if the truth emerges and this defence holds up.

Either way, one felt on reading City Press on Sunday that politicians and editors alike face a critical moment when they have to decide whether they will allow our politics and our journalism in fact, our national public debate to sink to such distasteful levels.

Harber is Caxton professor of journalism at Wits University.

With acknowledgements to Harber and the Business Day.