Jeremy Warner: Journalists don't reveal their sources. Accept it

At worse, sources' lives are threatened. They may also get jailed, fired, sued, or all three

Journalists don't reveal sources. This is such a key tenet of our profession, such a strongly held belief, that by now, in advanced democracies, the principle ought to have been accepted by governments, courts, parliaments and others that claim some kind of a proprietary right over information. Yet it is repeatedly challenged, generally on the basis that there is some kind of over-riding public interest - national security, law enforcement, commercial confidentiality and so on and so forth - in requiring disclosure.

Journalists don't reveal sources. This is such a key tenet of our profession, such a strongly held belief, that by now, in advanced democracies, the principle ought to have been accepted by governments, courts, parliaments and others that claim some kind of a proprietary right over information. Yet it is repeatedly challenged, generally on the basis that there is some kind of over-riding public interest - national security, law enforcement, commercial confidentiality and so on and so forth - in requiring disclosure.

I have personal experience of these matters. Soon after the launch of The Independent in the mid-1980s, I was required by the courts to disclose sources on a number of stories I'd written on City takeover bids. The circumstances and detail of the case were completely different to the one the BBC is embroiled in, and, to be frank, also of considerably less long term import. But the principle was exactly the same.

When a source who talks on the basis of anonymity is disclosed, it interferes with the free flow of information to the media, as those in the know will be more guarded in what they say to reporters if they think there is a danger of being unmasked. Outed sources nearly always face retribution of some form, even when they are performing an obvious public service in revealing information that powerful people don't want in the public domain. At worse, their lives are threatened, or they feel them to be threatened. They may also get jailed, fired, sued, or all three. At the very least, they are likely to suffer a dimunition in career prospects, as they are tainted as the untrustworthy employee, the official who cannot keep confidences.

It is already a dangerous-enough business being a press source for information those in authority don't want known about. All sources have to know that the journalists will go to the wire and beyond to keep their identity secret.

There are few circumstances I can think of which would justify a breach of the principle, and virtually none I can conceive of where the journalist would be justified in disclosing sources without permission.

The same goes for the process of elimination that official, "hunt the mole" investigations like to engage in. You know the sort of thing. If he's not your source, why don't you just say so and then he'll be off the hook. Elimination is just the thin end of a large wedge which ultimately ends in source identification. Andrew Gilligan, the BBC defence correspondent who reported the "sexing up" allegations, is therefore absolutely right to refuse to identify Mr Kelly as the source and to refuse to rule him out. The less a journalist gives away the better.

I'd got hold of information on takeover bids and gained a competitive edge over rivals by disclosing it first. The Department of Trade and Industry inspectors thought the information was also being used by others for insider dealing in the City - a criminal offence - and they wanted to know the identity of sources in the expectation this would lead them to the insider dealers. Their public interest, they argued, in pursuing the insider dealers was a higher one than mine in defending the principle of source anonymity.

I understood this argument, and was privately quite sympathetic to it. Even so, it would have been a betrayal to have disclosed the source and by breaching the principle I would have undermined the flow of information on stories where there obviously was a public interest in disclosure. In the end, the judge wisely decided he wasn't going to create a martyr, and fined me heavily rather than send me to jail.

Mr Gilligan's case is made difficult because he is dealing with an allegation rather than an absolute. Nobody disputed the information in my stories; merely the source's right to disclose it. If the allegations reported by Mr Gilligan are correct, then it plainly is very much in the public interest that they are aired. The case is at root not about the source's right of disclosure, but whether what he is alleged to have said is true.

The way events have unfolded demonstrates only too tragically just how destructive these mole hunts can be once the juggernaut of government and legal process gets underway. High principle and moral outrage become the order of the day on both sides of the argument, with little regard for those caught in the middle. For everyone involved, this is the most appalling outcome imaginable, but for the Government to have named a suspect in the way it did, was a gross misjudgement and an unforgivable act of prejudice, whatever the rights and wrongs of the case.