To change the controversy, change the question. In July 2003, Joseph C Wilson, a former US ambassador, wrote a New York Times article casting serious doubt on President Bush’s claim that Saddam Hussein had been seeking uranium in Niger. This posed the question: why did we go to war in Iraq?

A week later, a Washington Post columnist disclosed, on the basis of confidential briefings, that Wilson’s wife, Valerie Plame, was a CIA operative. Suddenly the question changed to: who is this man married to, and what is the couple’s agenda? As a distraction, it worked a treat: Plame’s career in intelligence lay in ruins, and Wilson’s revelation about the limitations of Saddam’s WMD programme was lost in a Washington soap opera.

The Damian Green fiasco exposes Theresa May as a trapped and wounded leader | Deborah Orr Read more

Compare the behaviour of Damian Green’s allies in the past three days. On 1 November, the writer and critic Kate Maltby reported that he had made sexual advances towards her in 2015 and 2016. Four days later, the Sunday Times reported that police had found pornography on a computer seized from Green’s parliamentary office in 2008.

On Friday, in a BBC exclusive on the Today programme, Neil Lewis, a former Scotland Yard detective, declared that he had “absolutely no doubt whatsoever”, after forensic analysis of the machine, that Green had accessed “thousands” of pornographic images.

The first secretary of state strongly denies all the allegations, which are now under investigation by Sue Gray, the Cabinet Office’s head of propriety and ethics. As her title suggests, her job is to establish whether Green behaved appropriately and in a manner befitting the de facto deputy prime minister.

Since Friday, however, his senior supporters have tried, with some success, to change the question. What they now ask, with the cold fury of Tories clutching Magna Carta, is whether the police are conducting a vendetta against Green, disclosing private information and politicising law enforcement.

Wrists have already been slapped and you can bet that further investigations will be mounted in the long-running feud between the embattled cabinet minister and the police. But let us not be so easily swayed by the studied outrage of the Green camp. It is perfectly possible that certain former coppers do not like him very much, but that what they have alleged is also completely true.

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On the question of Green’s allegedly epic consumption of porn, I imagine that if this is proved, most people will be wondering why an MP can get away with behaviour for which almost every employee in the land would be sacked. To put it crudely: does parliamentary privilege extend to the wrist? And if so, why?

What really matters, though, is that we do not lose sight of the broader picture. Gray has a formidable task. It is not her job to say whether or not MPs should watch smut in their offices: that unenviable responsibility is borne by Kathryn Hudson, the parliamentary commissioner for standards, who oversees the rules, and recommends action to the Commons committee on standards in public life.

But it is most certainly Gray’s job in this case to assess whether Green has told lies about his alleged consumption of porn, just as she must judge whether he is telling the truth about the alleged sexual misconduct.

If Green’s use of porn is proved, people will wonder how an MP gets away with acts for which they would be sacked

Full disclosure: I am a good friend of Maltby and was so at the time of the alleged incidents (though I did not hear about them until her decision to go into print). I am astonished by the suggestion that she is making these claims as a publicity stunt or to climb on a bandwagon. I mean, really: who would want, just for fun, to subject themselves to door-stepping by journalists, family intrusion and a two-page character assassination by the Daily Mail? Still, I recognise that I must recuse myself from this particular case.

It is widely assumed that Gray is considering only Maltby’s allegations. We don’t know whether this is in fact the case or whether there are other complainants. If there are, their allegations should also be addressed by the Gray inquiry. As I asked last month: was anyone now working in Downing Street warned about any allegations of sexual harassment against Green when he was appointed work and pensions secretary in July 2016, or to his current post in June? And if they were, how did they respond?

If you imagine that I write all this with relish, excited at the possibility of a ministerial scalp, you are dead wrong. For more than 20 years I have praised Green in writing and in person as one of the few senior Tories who grasped the need for root-and-branch reform of the party. In July, as most Conservatives made excuses and sought scapegoats for the party’s pathetic election performance, he had the clarity of insight to insist that “we need to think hard, work hard, and change hard.”

But that is precisely why there is such a strong sense of apprehension and anger among Conservative modernisers, especially women MPs and activists, who feel that Green may have betrayed utterly what they have fought for and what they believed he stood for.

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Since the long campaign to drain the poison from the Tory party began in the mid-90s, gender equality has been at its heart, as has the principle that those in power should not abuse it and that the Conservative aura of entitlement is one of the party’s gravest electoral liabilities.

Needless to say it will be a disaster for Theresa May if Green is not given a clean bill of health by the Cabinet Office inquiry. But it will also be a serious setback for those who have struggled for decades to persuade voters that the Tory party is not a tribe of self-serving sexists, bigots and xenophobes. If Damian Green is found to be a sex pest, what hope for the rest of them?

That’s the politics of the controversy. But the matter before Gray is one of simple ethics: did this man behave unacceptably towards women, and did he lie about that and other matters to the prime minister, the media and the public?

If he did, he will have to go. And if he does, he will not be the victim of a “witch-hunt”, a police stitch-up, or a smear campaign, but of his own conduct, his depleted sense of right and wrong, and his disloyalty to the very principles for which he once stood.

• Matthew d’Ancona is a Guardian columnist