The disturbing increase in state-sanctioned surveillance in recent years has generated much public debate, with many expressing concerns over intrusive tactics like phone-hacking, internet snooping and CCTV cameras on every corner. But in some cases, it can go much further than this. How much more intrusive and intimate would it be, for example, to be spied on by someone who shares your house, your bed, your life – maybe for as long as four or five years? To be secretly monitored by the father of your child?

The murky world of undercover policing has long operated outside the realm of public scrutiny, the nature of the work inevitably requiring a certain degree of secrecy. But a series of cases have recently come to light exposing a shocking absence of transparency and accountability around the practice, which constitute an incredibly strong case for a full, independent public inquiry into the rules governing the behaviour of those who go undercover – and those who give them instructions.

Since the unmasking of Mark Kennedy, aka Mark Stone, in 2011 and nine other undercover officers in the months that followed, worrying revelations have emerged about the apparent free rein given to police infiltrators to form long-term, intimate relationships with women in the groups they were sent to spy on.

Kennedy is one of those implicated in a legal case now being brought by eight women who claim they were duped into intimate relationships with undercover police. Another is Bob Lambert, aka Bob Robinson, who posed as a campaigner in the 1980s in order to infiltrate the Animal Liberation Front, two supporters of which were subsequently jailed for planting incendiary devices in two branches of Debenhams as a protest against the selling of fur. The culprit who planted a device in a third store was never caught.

Jon Murphy, the chief constable of Merseyside and the police chiefs' spokesman on undercover policing claims the forming of intimate relationships is "grossly unprofessional" and "never acceptable". But the women bringing the case have a copy of a letter from a Metropolitan Police solicitor that asserts relationships formed by a “Covert Human Intelligence Source” to obtain information are permitted and lawful under the Regulation of Investigatory Powers Act 2000 (RIPA) – a point reiterated by policing minister Nick Herbert in the recent parliamentary debate I hosted on this subject.

Despite the strength of the allegations against these men – Lambert, for example, reportedly fathered a child with a political campaigner in secret, and has admitted to a long-term relationship with a second woman – there has been virtually no attempt by the authorities to hold them to account. There has been no real debate about the human consequences for those women (or men, though I have yet to see such a case) of being conned into a loving, trusting relationship with someone acting under a false identity. And what of the children fathered by an undercover officer?

If this weren’t serious enough, new evidence about Lambert, which I detailed in my debate, has triggered further alarm about the personal conduct of those undercover – and the degree to which police officers are able to act as agent provocateurs. As is now on the parliamentary record, Lambert is accused by an ALF activist, Geoff Sheppard, who was jailed along with Andrew Clarke for the two Debenhams attacks in Romford and Luton in 1987, of planting the third incendiary device in the Harrow store.

If the allegations turn out to be true, then we must ask: can it be right that officers who commit a crime undercover should be able to do so with impunity? And to what degree are police spies permitted to cross the line of agent provocateur? The rules governing undercover policing are also worryingly deficient when it comes to giving false evidence in court to protect a secret identity.

Jim Boyling, for example, exposed last year for infiltrating groups such as Reclaim the Streets using the pseudonym Jim Sutton, concealed his true identity when he was prosecuted alongside a group of protesters for occupying a government building. The Met commissioner, Bernard Hogan-Howe, has defended the practice of undercover officers using fake identities in court, claiming there is no specific law forbidding it. Lord Macdonald, former director of public prosecutions, on the other hand, has called this position "stunning and worrying".

The public has a right to know why huge amounts of money are being spent on infiltrating campaign groups – with no apparent external oversight of the decision or whether the methods used are proportionate, or in breach of fundamental human rights. So far, the government response on these issues has been muted. The twelve different inquiries into undercover policing since January 2011 - each held in secret and looking at just one small aspect – have been completely lacking in oversight and far too narrow in scope.

Striking the right balance between safeguarding the public from genuine threats and protecting an individual’s right to privacy is one of the most difficult challenges facing any government. But the cases above point to a deeply worrying culture of ‘exceptionalism’ within covert operations – one which must be addressed through an independent and broad-ranging public inquiry into undercover policing. Only then can the government prove that it is committed to holding the police to account for their actions – in the past, present and future.