Up to 850,000 people in the UK pose a sexual threat to children, according to the latest National Crime Agency estimates.
Law enforcement officers have used a new method to calculate the size of the hidden population of criminals and estimate it at 550,000 to 850,000.
This includes pedophiles who download images of child abuse as well as those involved in direct physical abuse.
The new calculation method means the number is far higher than previous estimates that focused on the number of registered sex offenders and those who use dark internet websites to look at images of child abuse that are home to at least 300,000 people.
In its annual National Strategic Assessment, the NCA said plans to introduce end-to-end encryption for Facebook messages could affect their ability to catch pedophiles.
In one case, prolific offender David Wilson, a worker from King’s Lynn, Norfolk, used fake identities on social media to impersonate teenage girls and grooms and blackmailers to send him abuse pictures.
Information from Facebook and thousands of messages were key to his successful prosecution of 96 sex crimes against 51 boys, ages four to 14, for which he was incarcerated for 25 years.
The NCA assessment reads: “Information from Facebook and evidence with over 250,000 messages has been vital to Wilson when it comes to justice.
“However, end-to-end encryption plans prevent access to news content and likely mean other criminals like Wilson will go undetected.”
Lynne Owens, director general of the NCA, called on social media companies to block all opportunities for criminals to use their platforms.
She said: “While the NCA will continue to lead the fight against serious and organized crime, it is imperative that technology and social media companies match this intensity, increase security through design, and close all opportunities for criminals to take advantage of their platforms .
“In particular, we need to go to a place with no tolerance for the presence of such material on the Internet in order to raise the bar for insults and, above all, to protect children.”
Child abuse is a type of crime that, according to the NCA, is believed to be increasing, compounded by the increase in online activity due to bans during the pandemic.
In March 2020, when restrictions began, the NCA began cracking down on high-harm sex offenders and by the end of the year had identified more than 1,000 suspects, arrested 320 people along with police and protected more than 400 children.
Of the 320 arrested, 122 were affected by the NCA, including 17 people in trust, including the deputy head of an elementary school who was later detained.
Other forms of crime believed to be increasing include bribery and corruption, cybercrime, drug trafficking, fraud and money laundering.
Ms. Owens said there had been a surge in ransomware attacks during the pandemic, computer software that was used to block access to a particular system until a ransom was paid.
She said: “The threat (from organized crime) has been shown to be resilient in the face of Covid-19. The perpetrators are increasingly turning to online rooms and using new technologies and established tools to avoid detection.
“As a result, we’ve seen a dramatic increase in ransomware attacks and increasing levels of cyber-enabled fraud.”
The NCA also said sales of software for remote access to someone else’s computer “increased significantly” as the number of people working from home increased.
Currently, the NCA estimates that 69,281 people are involved in serious and organized crime in the UK, although it is believed that this estimate can increase when information is accessed from local databases.
A key operation in 2020 followed the successful hack of the Encrochat secret service by the French authorities, which was used by organized criminals to hide their activities.
In the UK alone, the information provided resulted in 1,550 arrests and seizures of 5.8 tonnes of Class A and B drugs, nearly £ 57 million in cash, 115 firearms and 2,879 rounds of ammunition.