Newcastle prosecutors said the Northumbria police paid the man - referred as "XY" and only identified as a British Asian man - more than $12,500 over 21 months to find out the times and whereabouts of parties where girls were being given drugs and alcohol before they were abused.
The child rapist paid £10,000 by police to spy on parties where they suspected girls would be abused is facing a "real threat" to his life, it has been reported.
"But, I have questioned the chief constable and, in liaison with other senior officers, Mr Ashman has satisfied me that the hard moral decision to use the informant was taken with care and with particular regard to the welfare of victims".
Vote now and contribute to the debate by leaving a comment below.
XY told the court that he was asked by the police to provide information which would lead to a conviction.
"It beggars belief it would ever have been considered, let alone approved".
'I should never have been dragged into that courtroom for people to see me'.
"You just couldn't make it up", Jon Brown, head of development at NSPCC, told the Guardian. The use of such a person by the police has been widely criticised by organisations such as the NSPCC that otherwise would be expected to cheer the careful and effective way the network was uncovered, its victims supported - to the point where 20 of them felt able to give evidence - and so many prosecutions were secured.
One of the defendants, who has been jailed for ten years, told his wife he was going night fishing before he picked up a drunk 15-year-old on the street and raped her.
'However good the force's intentions, their misguided actions run entirely counter to all current child protection procedures and what we know about sex offenders and could have compromised this investigation'.
She said: "They told us what she would do for them for money and drugs or she'd get battered".
But Judge Penny Moreland rejected his evidence in its entirity, describing it as "inherently unreliable" and "clearly dishonest".
"But I'm very, very surprised at this as a tactic".
'No matter what I do, it will affect my family'.
He said: 'They (the police) would not show me their badges.
"But when it comes to child sexual abuse, I've prosecuted offenders in their 70s and 80s - they don't change their behaviour invariably".
'I didn't know if they were there to protect me. "These victims have had to endure multiple abuse and multiple failings of those who are tasked with safeguarding them". Yes, I may have had a bad past but when I left prison I tried to make a difference.
However he also said he "was not allowed to be open and honest".XY had become agitated during his evidence and even shouted "f*** off you divvy" to one of the defendants during the hearing.
Defending barristers argued that the public's confidence in the justice system would be undermined if the trials went ahead, given that the rapist XY had acted as an informant, formally known as a Covert Human Intelligence Source, or "CHIS".
That said, whilst the use of such a high-risk informant may have diverted us from celebrating the outcome of the case, there is no doubt that the simplistic "end justifies the means" argument, which has been deployed in a knee-jerk defence of the police action misses the point. The force's handling of XY was investigated by the IPCC, which found no misconduct and made no recommendations.
"However in the case of XY it is clear that his relationships with others have allowed the police to prevent and detect some of the most serious crimes occurring in our communities, this would not have been possible through conventional methods".
"My thanks and those of the people of Northumbria go out today to these fearless women for the tremendous fortitude they showed in relating their often appalling experiences to the court and enduring cross examination in order to convict risky sex offenders".