Britain's biggest police force witnessed a 700% spike in the number of online child abuse cases referred to them by national investigators over three years, an inquiry has heard.
The National Crime Agency (NCA) alerted Scotland Yard to potential paedophiles operating over the internet on 647 occasions between January 1 and September 30 in 2017.
This marked a jump of 700% since 2014, the national child abuse inquiry was told, fitting a pattern of "almost year-on-year" increases across all forces.
Child abuse investigators at the NCA also received more than 30,000 tip-offs from a US monitoring group about online predators in the UK during just one year, it was heard.
The Independent Inquiry into Child Sexual Abuse is holding public evidence hearings to examine how the internet allows sex offenders to target youngsters.
Jacqueline Carey, counsel to the inquiry, said in her opening statement: "On any view, whichever way the statistics are looked at, there has been a marked increase in the last five years in relation to online-facilitated child sexual abuse.
"The panel may wish to consider whether that is a trend which is likely to continue for the foreseeable future."
Sexual offending online can include the use of the internet to force a child to take part in or witness sexual activity, grooming them online for abuse or posting indecent images.
Setting out the escalating problem, Ms Carey pointed to a rise in referrals to the NCA by the National Centre for Missing and Exploited Children (NCMEC).
Referrals from the US-based organisation about offenders they had identified with IP addresses in the UK shot up from 1,591 in 2009 to 30,661 in 2016.
A single tip-off could contain information about multiple offenders or victims, up to 5,000 child abuse images linked to a single UK user or thousands of IP addresses linked to one offender or victim, the hearing was told.
It is then investigated by the NCA's specialist team at the Child Exploitation and Online Protection Centre, who pass information on to local forces when they can pinpoint offences to a geographical area.
Police forces in England and Wales recorded 5,653 incidents of sex crimes against children which had an online element in 2016-17, up from 3,903 in 2015-16, according to the NSPCC.
The Metropolitan Police had 333 crime reports relating to online child sexual abuse during 2016, which "seemed to increase just after periods of school holidays", Ms Carey said.
It was found that 90% of victims were female and the average age of the victim was 13.
The Internet Watch Foundation, a UK-based safety watchdog which flushes out abuse pictures and videos online, passed on information about 35,000 indecent posts to websites as of October 2017.
However, much offending was said to occur on the dark web, which allows users to browse anonymously.
Around 80% of traffic on one browser, The Onion Router (Tor), was found by researchers to end up on sites with names that indicated it had indecent images of children.
The IICSA also commissioned its own research into the issue, finding one in 10 adults have had a sexualised conversation with a child.
Evidence sessions will be held for five days this week.
Copyright (c) Press Association Ltd. 2018, All Rights Reserved. Picture (c) PA Wire.