In an age of declining press influence, the Daily Mail's success in forcing its story on the "links" between Labour figures and a paedophile rights group (which is not a new one) onto the national news is a reminder of how Fleet Street can still set the agenda. Labour's initial response to the Mail's splash last Thursday, which branded Harriet Harman, Jack Dromey and Patricia Hewitt "apologists for paedophilia" over their alleged support for the now-defunct Paedophile Information Exchange (PIE) in the 1970s, was to ignore it (in common with the rest of the media). But after the Mail led twice more on the story, and columnists in other papers, including the Observer and the Sunday Mirror argued that there were questions to answer, the party broke its silence yesterday.

In response to a question from Sky News, Ed Miliband said of Harman, who, as the party's deputy leader, is the most senior figure targeted: "I have known her for 20 years. I do not set any store by these allegations. I know she has a long and proud record of being on the right side of all of these issues." This was followed by a lengthy statement by Harman herself and one from Dromey, her husband and the shadow policing minister (Hewitt has remained silent). Then, last night, in the most public intervention from any Labour figure yet, Harman gave an interview to Newsnight (which you can watch in full above) devoted to the story.

While rebutting the central charge that she was a supporter of PIE during her time as legal officer for the National Council for Civil Liberties (the predecessor group to Liberty), and the claim that she sought to water down a ban on child pornography, Harman also moved from defence to attack. She declared of the Mail:

It is ironic that they're accusing me of supporting indecency in relation to children when they themselves are not above producing photographs of very young girls, titivating [sic] photographs in bikinis, so, you know, I stand by what I was doing at NCCL and I stand by what I was doing all the way through.

And added: "If there's anybody, over the years, who has supported indecency, it is much more the Daily Mail than it is me - and that's the frank truth of it."

After the Mail's disastrous attempt to smear Ralph Miliband as "the man who hated Britain" (which Labour believes explains the paper's current vitriol), the party's figures are more confident than ever in questioning its moral legitimacy and Harman (invariably referred to as "Harperson" in its pages) has more reason than most to challenge its authority. In his recent profile of Paul Dacre for the NS, Peter Wilby published this memorable charge sheet:

This year, the Mail reported that disabled people are exempt from the bedroom tax; that asylum-seekers had “targeted” Scotland; that disabled babies were being euthanised under the Liverpool Care Pathway; that a Kenyan asylum-seeker had committed murders in his home country; that 878,000 recipients of Employment Support Allowance had stopped claiming “rather than face a fresh medical”; that a Portsmouth primary school had denied pupils water on the hottest day of the year because it was Ramadan; that wolves would soon return to Britain; that nearly half the electricity produced by windfarms was discarded. All these reports were false.

But Harman's fightback was marred by her failure to express explicit regret for the rules which allowed PIE to affiliate itself to the National Council for Civil Liberties (which is not, of course, the same thing as the NCCL endorsing the group). Rather than simply conceding that the NCCL was wrong to allow itself to be infilitrated in this manner (as Liberty director Shami Chakrabarti has previously done), Harman embarked on a convoluted explanation of the relationship. She said: "They paid their money to NCCL and, at the time...well, NCCL takes money from any organisation which was a lawful organisation and any individual."

She went on to reassure viewers that the group held no sway in the NCCL but failed to simply declare that it was wrong for the potential to exist at all. This morning, Harman corrected that omission, with an aide stating: "She regrets the existence of PIE and of course she regrets any organisations' involvement with them including the NCCL. But she does not regret joining the NCCL. By the time she arrived, (PIE) were very much under the radar."

Harman's reluctance to issue anything resembling an "apology" was understandable. It risked being seen as an admission of guilt and as a validation of the Mail's smears. After banking her "apology", the Mail would next demand her resignation. But while now expressing appropriate regret for the NCCL's past laxity, Harman is, crucially, not retreating from the battlefield. She stands by her accusation that the Mail publishes "indecent photos" and "will not take lectures from them". On this point, she is entirely right. Rather than merely challenging the message, it is essential to challenge the messenger too. The Mail's deeds, both past and present (from "Hurrah to the Blackshirts" to "The man who hated Britain"), mean it is standing on the thinnest moral ground.