A number of people who claim they were tricked into forming intimate relationships with undercover officers from the Metropolitan Police are taking legal action against the force.
Eleven women and a man are reportedly seeking damages for emotional trauma following allegations that specialist officers infiltrated environmental activist groups and engaged in sexual relationships with members.
Their cases have been lodged in the High Court, but the Metropolitan Police has launched a counter-claim arguing that some cases should be hard by the Investigatory Powers Tribunal, according to The Times.
The judicial body, formed in 2000 by the Regulation of Investigatory Powers Act (Ripa), holds a number of hearings in private and has no obligation to take oral evidence.
Some of the claimants say they had relationships with Mark Kennedy, the undercover police officer who spent seven years spying on environmental activists posing as long-haired drop-out climber Mark "Flash" Stone.
One woman, who claims one of the undercover officers fathered her child, is also planning a landmark legal claim that will test whether the Met should bear some financial responsibility for its upbringing, according to The Times.
A Scotland Yard spokesman said: "They are very unusual and complex areas of law - our legal position is that the Investigatory Powers Tribunal is the proper authority to hear these cases because of the nature of them and the evidence involved, but the decision on this will be taken by a judge."
Only half of the claimants face the Met's challenge as the other alleged relationships took place before the Ripa was introduced, it is said.
Solicitor Harriet Wistrich, who is representing the women, told The Times: "These women are suing for a gross invasion of privacy and the Met's response it to try and hive it off into a secret court."