Paying £10,000 to a convicted child rapist to infiltrate a paedophile gang “crossed a line”, it has been claimed.
Jim Gamble, who set up the Government’s taskforce to fight child sexual exploitation, criticised the move by Northumbria Police.
The force’s chief constable had defended the decision, saying dangerous men would not be behind bars if he had not decided to pay the offender to spy on parties where it was suspected under-age girls were fed drugs and sexually abused.
But Mr Gamble, former chief executive of the Child Exploitation and Online Protection Centre, said the tactic went “way over the line”.
He told the BBC: ‘I think all police forces are under pressure to get things right.
‘But there are ways and means to doing it ... there need to be limits and there should be lines that shouldn’t be crossed.
‘Personally, I can’t envisage any circumstances where I would have authorised payment to someone convicted of rape.’
The informant, known only as XY, was recruited despite being a sex offender who had drugged an under-age girl and invited another man to rape her after he had done so, Newcastle Crown Court heard.
Years later, the force recruited him to work as an informant on the massive Operation Sanctuary inquiry, one strand of which, known as Operation Shelter, has just finished going through the courts.
A total of 461 people have been arrested as part of the investigation, while 782 potential complainants have been spoken to and 278 victims have been found.
Defending the deployment, chief constable Steve Ashman told a news conference: ‘It’s a decision that we’ve had to wrestle with ourselves but I can categorically state sitting here today that there are dangerous men behind bars now and vulnerable people protected that would not have been the case had we not used that informant.
‘This is the world that we have to step into in policing and it is dangerous and it is difficult but that is what we are prepared to do.
‘We’ll do everything we can within the law to bring these people to justice.’
Mr Ashman insisted the parameters stated XY was not to be sent to attend parties, although he could not be 100% sure the informant stuck to those rules.
Jon Brown of the NSPCC said the charity was ‘appalled’ by the revelations.
He said: “We are appalled to learn that police paid a child rapist and planted him in the midst of vulnerable young girls.
‘It beggars belief that it would ever have been considered, let alone approved, and serious questions must be asked about the force’s approach to child sexual exploitation operations.’
The wider operation has seen around 100 people convicted of a range of serious offences, including drugs, modern-day slavery and firearms charges, with jail terms totalling more than 300 years.