Read between the lines: this is press censorship Tomorrow in the House of Lords, ministers will try to excise from the Defamation Bill wrecking amendments inserted by peers who are determined to impose on newspapers a draconian version of Lord Justice Leveson's proposals for press regulation. If they fail to expunge the amendments, the revised Bill will create in the UK a version of prior restraint - censorship before publication - that has not existed in this country for 300 years and that is explicitly outlawed by the First Amendment to the US Constitution and the European Convention on Human Rights (ECHR). Not satisfied with prior-restraint alone, the wreckers also wish to punish newspapers that do not submit to state-sanctioned regulation by obliging them to pay exemplary damages if defeated in actions for libel or invasion of privacy. Like Sir Brian Leveson, they attach too little weight to the possibility that this might breach Article 10 of the ECHR. Such restrictions of liberty might please victims of tabloid misbehaviour, such as Max Mosley and Hugh Grant, but it would give the Government no choice but to kill the Bill. This would be regrettable, because it is valuable. Its originator, Lord Lester, an eminent human-rights lawyer, describes it as "a charter not for the press but for the public." In fact it is valuable to both groups, which is why it has the support of newspapers and campaigners who wish to open the libel courts to less affluent litigants. Supporters of the contested clauses claim noble purpose. But, by attempting to hijack Lord Lester's work as a vehicle for state-sanctioned regulation, they have shown that, for them, ends justify means. Their actions reveal something more significant, too. Throughout the phone-hacking scandal, the Leveson Inquiry and the controversy spawned by the Leveson Report, supporters of state-sanctioned newspaper regulation have promoted the idea that they are virtuous servants of the public interest. Their abuse of the Defamation Bill has revealed a less wholesome reality. The Hacked Off campaign and its supporters should take note: the antics in the Lords have revealed the presence in Parliament of opinions it suits them to pretend do not exist. Vulnerable to the accusation that a press law, once enacted, might be strengthened rapidly, they say limited statutory backing for a new system of regulation would not be extended to impose tougher controls. They accuse Leveson's opponents of imagining the slippery slope down which we believe Britain's press laws would slide if his proposals were implemented. The use made of the Defamation Bill by Leveson-supporting peers, such as Lord Puttnam and Baroness Boothroyd, has exposed such views as misguided. I hope this useful and progressive Bill can be rescued and enacted with the support of both Houses. But whether it lives or dies, it has already performed service to the causes of liberal democracy and press freedom. Britain needs self-regulating newspapers untrammelled by a statutory backstop because there are already in Parliament men and women who believe they are entitled to impose upon others their values and their ideology. To believe that such well-intentioned meddlers will become less bold in future is wishful thinking. They exist and have made it plain that they could exploit a minimalist piece of legislation to neuter newspapers entirely. We have been warned. Any press regulator supervised or empowered by legislation would give politicians a tool to extend control over the press. Some of them have now shown us how willing they would be to use it. They would not call it censorship. They would believe they were acting in the public interest. If they shared any of the hubris shown by the peers who amended the Defamation Bill, they might sincerely believe it. Those who consider press freedom and liberty inseparable should not trust them. They need only win once. If we are to preserve liberties that have endured for centuries and made this country a beacon of democracy, we must win every time. The writer is professor of journalism at the University of Kent and author of the pamphlet "Responsibility without Power: Lord Justice Leveson's constitutional dilemma"