One teen chat app has featured in more than 1,100 child sexual abuse cases in the last five years, the BBC has found.
Of 29 police forces that supplied information to the BBC, all but one had child exploitation cases involving Kik.
Police say they are frustrated with Kik's response, with one detective saying getting information out of the firm was a "bureaucratic nightmare".
Kik said it was "constantly assessing and improving its trust and safety measures".
A BBC Freedom of Information request sent to all 47 police forces in the UK revealed there had been 1,147 investigations by 28 forces into offences of child sexual exploitation, grooming and image offences involving the app. Eighteen forces failed to supply any information.
Founded in 2009, Canada-based Kik claims 300 million users worldwide access its free instant messaging service.
It is popular with teenagers, has many anonymous accounts and is easy to sign up for using false details.
'A brick wall'
Constable Jason Cullum from Northamptonshire Police's paedophile online investigation team told the BBC delays due to the "bureaucratic nightmare" of obtaining information from the company put children at further risk.
He is investigating a complex grooming case involving more than 90 profiles - some suspected offenders, others child victims - but he needs information from Kik to identify and trace them.
Police officers contacting Kik are given an automated response and directed via a complex legal process - under the Mutual Legal Assistance Treaty (MLAT) - to gain a court order.
"It's incredibly frustrating. We're banging our heads against a brick wall," said PC Cullum.
"There's a child that's going to be abused for probably another 12 months before we know who that is."
Canada and the US have strict rules on releasing personal information to law enforcement agencies to protect individuals' privacy.
Kik says it will release some information if there is an "imminent threat of death or serious physical injury to any person".
In these cases, the app will release "limited basic subscriber data".
Home Secretary Sajid Javid has threatened to take action against tech companies if they do not help to tackle online child abuse.
"The threat has evolved a lot more quickly than the industry's response and industry has just not kept up," he said.
"So let me say this - I'm not just asking for change, I am demanding it."
'Behind closed doors'
Taylor was a lonely and vulnerable 13-year-old when the abuse began on Kik.
"It started with a lot of selfies... but it would escalate to underwear photos... naked photos, then videos."
Taylor told the BBC that more than 100 men, possibly 200, made contact through the app. Taylor criticised Kik for not doing more to protect vulnerable users.
"It's all going on behind closed doors, they can see it but they're not doing anything about it. That's what upsets me."
In a statement, Kik told the BBC: "We take online safety very seriously, and we're constantly assessing and improving our trust and safety measures."
It said it will continue to "provide resources to parents and strengthen relationships with law enforcement and safety-focused organisations".
But PC Cullum said he was not reassured and that abused children remained at risk.
He said: "In this day and age I should be able to identify everyone, but I can't."