Leading article: We need to find our way to a new balance of liberties

This has already been a momentous week in the titanic clash between the champions of transparency and the protectors of privacy. On Monday, the subjects of a string of super-injunctions were defied by an anonymous Twitter user. That was followed yesterday by the failure of the former motor-sport boss, Max Mosley, to persuade the European Court of Human Rights that newspaper editors should notify the targets of their exposés before publication. On the face of it, those were two blows for transparency. But the champions of privacy had something to cheer when the Press Complaints Commission ruled yesterday that The Daily Telegraph breached industry rules when it covertly recorded Liberal Democrat ministers.

So which side deserves to win? This is treacherous ground. Transparency and privacy are both important public goods, but are often in conflict. Yet certain broad principles provide a guiding light. First, as David Cameron argued last month, the broad parameters of privacy and press freedom should be decided by Parliamentarians, rather than by judges. In this respect, the ECHR's rejection of Mr Mosley's plea is welcome. The idea of a pre-publication notification rule might, or might not, have merit, but it should be for MPs, not judges, to decide whether it should be introduced.

Second, there needs to be adequate protection for investigative journalism that serves the public interest. The PCC was right to rule that The Telegraph sting failed to meet that standard. But there are cases when the public interest does merit intrusion. The super-injunction (a legal order which prevents the media reporting on its very existence) provokes serious concern in this regard. This has been used not only by celebrities to keep embarrassing personal information from the public domain, but also by companies (notably the oil trading firm, Trafigura) to protect their reputations.

That said, the use of Twitter to defy super-injunctions this week does raise difficult questions about the divide between old and new media when it comes to defamation. Jemima Khan claims that she has been falsely accused of having an affair on the site by the same user who published the names of those who have taken out super-injunctions. This does seem to make a mockery of the protection of reputations that the laws of defamation are designed to ensure. Internet companies have managed to avoid prosecution for libel. But an increasing number of people get their news online. As the Culture Secretary, Jeremy Hunt, indicated yesterday, the law does need to keep up with the change in the manner in which the public consume information if our defamation laws are not to become toothless.

Yet we have to recognise the practical difficulties of trying to police the internet. In one sense, to hold companies such as Twitter accountable for comments by their users is like holding BT responsible for what people tell each other on the phone. There are clashing international jurisdictions too. The US has had to act to protect its writers from Britain's draconian libel laws. Co-operation from the American authorities on censoring Twitter is unlikely to be forthcoming. And how far should the net be cast? There have been calls in recent years to censor Google. But we have to consider what we would lose by going down such a route. Even if it could be done, what would be the social cost of shackling the internet?

We are fumbling our way in the dark. And self-interested, sometimes unscrupulous, individuals are forcing the pace. We look to politicians and judges to attempt to strike a balance between competing concerns over freedom of expression, the right to privacy and the state's powers of censorship, while keeping the public good firmly in mind. It is an unenviable job, but attempt it they must.