Officers warned Hunters Online to stop pretending to be teenagers on website apps to catch paedophiles red-handed.
Ryan Donaghey, one of the team behind Hunters, said they would comply with the police.
But he defended the group’s activities saying “online grooming is a big problem and not enough is being done about it”.
Hunters Online describe themselves as “a group of people aiming to make our children aware of online grooming and paedophiles”.
Dad-of-one Mr Donaghey, a self-employed DJ, and events promoter, said Hunters was set up by himself and a group of like-minded volunteers from across the UK.
Since their page went live a month ago, Hunters has gained more than 2,000 ‘likes’.
Mr Donaghey’s Crimewatch-style webcam videos warning people about child sex offenders and the dangers to kids of online apps have been viewed thousands of times.
The police warning came after Hunters posed as a 15-year-old girl on an internet app and a 28-year-old man began to talk to them. The conversation was broadcast live on the group Facebook page and watched by horrified parents.
“The viewers wanted to see how far this individual would go,” said Mr Donaghey.
“The guy said ‘come and meet me at a club in Manchester’.
“We replied saying ‘I’m 15 years-old, I can’t’.
“He said he’d ring a taxi for her, he was pushing for ‘the ‘girl’ to meet him. He started going in depth about what he wanted to do to this girl. It got a bit dangerous.
“I felt out of my depth so I called the police straight away. We had all this evidence. They were very helpful, but they didn’t know enough about what I was doing and if any laws had been broken so they told us to stop doing it.
“We will take that on board. We don’t want to disrespect the police.
“We understand the police don’t like people doing this because it could put people in danger.
“But we find that the police have different opinions across the country. Some have told us we’re not breaking any laws so what are we doing wrong?
“I want to tell parents to be careful. You can go on these apps and within 10 seconds guys will pop up and start conversations like this. I really want to bring awareness to it.
“I would advise all parents to check their children’s phones and if there is an app on there they don’t know, delete it.”
Hunters is trying to raise money through crowdfunding for a poster campaign.As we went to press they had raised £75 towards a target of £1,000.
“I feel there isn’t enough going on to deal with this kind of behaviour,” said Mr Donaghey.
“There are campaigns about drink driving and no smoking, but where are the campaigns to stop online grooming?”
He said Hunters was a not-for-profit page run by volunteers.
A statement on the Hunters page says: “When conducting our investigations, we never approach anybody first.
“Instead, we set up a profile and wait for messages. When we receive a message, we reply immediately and tell them that we are underage.
“When talking to anyone, we always try to avoid sexually explicit conversation. We act young and uneducated on the subject, and we NEVER encourage sexual chat or sexual behaviour.
“Some people are sceptical about what we do and how we do it. We’re not vigilantes who operate above the law, we’re concerned citizens who work closely with the police to help effect change and to keep our children safe! We will continue to work to catch these sexual predators who terrorise our children, and we’ll do our best to bring awareness to the epidemic our children are facing online today.”
A police spokesman said: “We urge absolute caution before anyone considers such activity and would ask that people have confidence in the police and other law enforcement in our prioritisation in tackling grooming and child abuse whether that be on or offline. We would always ask the public to contact us at the earliest opportunity if they suspect such behaviour rather than take the law into their own hands.
“We do not encourage the public to act as ‘Agent Provocateur’ in order to entrap offenders.
“When they do such, individual activities can have significant pitfalls such as the potential to compromise on-going investigations, which could in turn negate or compromise months of investigative work.
“The activities can also cause vulnerable individuals to be placed at serious risk of harm.
“Whilst we understand the concerns regarding the internet activity of paedophiles and subsequent dangers that they present to children, we can assure members of the public that we are committed to targeting dangerous offenders be it online or elsewhere.
“The police act both covertly and overtly to identify online criminality on a daily basis, as well as working work closely with partners to ensure that children are educated regarding the risks posed online.”
Further information on staying safe online is available at http://www.ceop.gov.uk/ http://www.thinkuknow.co.uk/ and http://www.getsafeonline.org.uk/