Police spies are still being given "free rein" to have sexual liaisons, say the eight women suing Scotland Yard over claims they unwittingly had long-term relationships with undercover officers.

The eight have criticised the government for failing to ban undercover officers from striking up sexual relationships with the targets of their surveillance.

They say they have suffered enormous emotional trauma after discovering that the men they had been in relationships with for years were undercover officers who had been sent to spy on political groups.

The women added that the failure "to introduce measures to prevent further abuse amounts to institutional sexism".

The criticisms were made in response to a Home Office consultation which will draw up an updated code of conduct governing the deployments of undercover police officers.

Damian Green, the policing minister, said that controls over undercover police deployments were being strengthened following a series of controversies.

This month the home secretary, Theresa May, ordered a public inquiry into the undercover infiltration of political groups following revelations that a covert unit, the Special Demonstration Squad, had spied on the grieving family of Stephen Lawrence.

The women began legal action after they discovered that they had had intimate relationships lasting up to six years with undercover officers, including Mark Kennedy, Bob Lambert, Mark Jenner and John Dines.

Lambert, who pretended to be an environmental and animal rights activist for five years, fathered a child with an activist, but left both when he ended his covert deployment.

Police chiefs have insisted that the undercover officers were not permitted "under any circumstances" to sleep with people they were spying on.

Over the past two years, police have hired lawyers to block the women's legal action in the courts.

In their response to the consultation, the women said: "We note that despite the controversy over the issue of undercover relationships in the past couple of years, the codes of practice fail to make any mention of intimate and sexual relationships.

"Having had our privacy intruded upon to a huge and damaging degree we feel that these guidelines fail to address the issues raised by our claims and fail to offer any increased protection to the public."

They added: "The situation as it stands currently gives free rein to officers and their handlers."

Jenny Jones, the Green peer, backed the women's stance and called on the government to "explicitly rule out undercover police from engaging in sexual relationships" to "prevent the police from making the mistakes of the past".

Prosecutors are considering whether to charge three as-yet-unnamed police officers over sexual relationships they formed while undercover.