Imagine the scenario. You meet someone and, from the outset, the attraction is mutual: silently shared smiles, lingering glances. You bond over shared interests and worldviews, and exchange telephone numbers. You start sleeping together and – as your pulse quickens every time the phone rings – you realise you are falling for each other. Days are spent together, walking in parks, trips to the cinema, romantic meals; time apart becomes difficult. Eventually, your partner moves in, and for years you share everything. Maybe you even have a child together. Then – suddenly – they appear depressed and become distant. One day, they are gone, leaving only an apologetic note on the kitchen table. You then discover everything you knew about them was false. They have invented a fake identity; their backstory, opinions, entire life, all a lie. They are undercover police officers, and were sent to spy on you and your friends.

It sounds like a dystopian fantasy belonging in the Stasi archives of former East Germany. But this is the experience of several British women who are pursuing a civil case against the Metropolitan police. Last week, the Crown Prosecution Service ruled that four undercover police officers who spied on activists would not face sexual offence charges, including rape, sexual assault, sexual intercourse by false pretences, as well as misconduct in public office. These women consented to sleeping with men they believed were fellow activists, not police officers spying on them – and yet the CPS believes there is “insufficient evidence” for a prosecution.

What we are witnessing must surely be a stitch-up over what the women believe amounts to being raped by the state. The phone-hacking scandal rightly provoked widespread condemnation on the grounds that it was an impermissible violation of privacy. But what about police officers who share their lives with women, have sex with them, and – in at least two cases – fathered children with them? No wonder one of the women involved describes the practice in chilling terms as “body-hacking”. The difference is, of course, that the women involved are activists fighting for environmental and social justice: the sort of people who enjoy very little sympathy from those with power and influence.

The response of the authorities is riddled with contradictions. The CPS might have judged that there is not enough evidence to charge the police officers with misconduct in public office. But Jon Murphy – the Association of Chief Police Officers’ spokesman who deals with undercover operations – has claimed such relationships are not permitted “under any circumstances” and amount to “grossly unprofessional” behaviour.

The Metropolitan police commissioner, Sir Bernard Hogan-Howe, taking another tack, claimed sex with activists was not “part of the strategy” but was simply inevitable. And Nick Herbert – a former Home Office minister – declared in the Commons in 2012 that sex with members of “the group targeted” could be permitted. But surely allegations of rape and sexual assault should be treated seriously, and if individual officers are not even charged with misconduct in a public office, then the focus should move on to those employing them to spy undercover.

One of the women involved tells me that, in a sense, she is conflicted about the CPS judgment. On one hand, if the officers had faced charges, it would have drawn “a very clear line in the sand”, deterring future officers from having sex under false pretences on the basis that a rape charge could await them. But her understandable fear is that the individual could take the flak, leading to the conclusion that the institution is clean. Rather than being treated as a systemic problem, a defence of individual misconduct – of a few “bad eggs” acting beyond orders – could be used instead. It is certainly fanciful to imagine that undercover police officers’ handlers were unaware of long-term relationships being established with activists they were spying on.

There are real grounds for believing the CPS has its own reasons for wanting to move on from this scandal. There are those who suspect that the CPS is itself implicated. In 2011, Guardian investigative journalists Rob Evans and Paul Lewis covered a case in which the CPS used tapes recorded by police officer Mark Kennedy – who spent seven years masquerading as an environmental campaigner – in a prosecution which had to be abandoned, as a result of the tapes being suppressed, not disclosed to lawyers for the accused. The CPS hired Sir Christopher Rose – the chief surveillance commissioner – to investigate the claims, leading him to conclude that only one junior prosecutor in the East Midlands was involved. But a 2012 Independent Police Complaints Commission report revealed emails suggesting that very senior prosecutors in London knew about Kennedy’s evidence.

In March 2014 the home secretary, Theresa May, announced a public inquiry into undercover police officers after revelations that the family of Stephen Lawrence had been spied on by the Met. Its remit must surely include examining the role of the CPS. One of the women has voiced a concern that the public inquiry will concentrate above all else on the horrifying appropriation by undercover police officers of the identities of dead children; another concern is that only the Special Demonstration Squad, a murky unit that existed between 1968 and 2008, will be examined.

In the meantime, the women are suing the Met for emotional trauma. Alison is one of the women: she had a five-year relationship with Mark Jenner, who lived with her for four years. “I thought it was one of the best relationships in my life,” she tells me. “In a matter of weeks after he left, it turned into one of the worst nightmares. I had been living with him, sharing a life with him, and thought I had a future with him: it all just dissolved.” But the women are survivors and fighters, not victims. “The irony is they’ve thrown together some of the most able, most passionate, brightest activists in one group,” she says.

This case will not attract the attention of the supposed rightwing libertarians who rail against state intrusion into the lives of the individual. These inspiring and courageous women are up against a highly resourced state that looks after its own. They deserve support and solidarity. As they are aware, this is not simply about their own traumas. It would be naive to imagine that the police – institutionally averse as they are to dissent – are not spying on those they regard as troublemakers as well as alleged terrorists. Other opponents of the status quo could today be forming relationships, sharing lives and beds with those spying on them. That is why this institutional conspiracy must be confronted head-on.

• This article was amended on 25 August 2014. Due to a subbing error the original article stated that Alison, one of the women suing the Met for emotional trauma, had a relationship with Mark Kennedy, which was not the case.

