The home secretary has called for the social media giant to reconsider its plans, with concerns child safety measures are inadequate to protect youngsters from online grooming.
Currently, 800 predators a month are arrested by UK law enforcement agencies and up to 1,200 children are safeguarded from child sexual abuse following information provided by social media companies.
The National Crime Agency (NCA) estimates 92 per cent of Facebook Messenger and 85 per cent of Instagram Direct referrals could be lost if Meta proceeds with its plans to “go dark” – meaning thousands of criminals a year could go undetected.
On Wednesday, Ms Braverman urged Meta to urgently commit to installing safety measures to protect children from vile attackers, or halt the planned rollout altogether.
The appeal follows a similar intervention in July, when she wrote to Meta boss Mark Zuckerberg expressing her concerns about the planned rollout.
Ms Braverman said: “The use of strong encryption for online users remains a vital part of our digital world and I support it, so does the government, but it cannot come at a cost to our children’s safety.
“Meta has failed to provide assurances that they will keep their platforms safe from sickening abusers. They must develop appropriate safeguards to sit alongside their plans for end-to-end encryption. I have been clear time and time again, I am not willing to compromise on child safety.
“We all have a responsibility to do what we can to tackle this devastating crime, and I urge them to work with the government.”
Meta-owned messaging app WhatsApp already offers end-to-end encryption by default, which prevents anyone other than the sender and recipient of a message from accessing its contents.
The social media giant is planning to add the feature to both Facebook Messenger and Instagram Direct chats later this year.
National Crime Agency (NCA) director of general threats, James Babbage, said if the company introduces end-to-end encryption as planned it will “massively reduce our collective ability” to protect children.
“We are not asking for new or additional law enforcement access, we simply ask that Meta retains the ability to keep working with us to identify and help prevent abuse,” he said.
“This collaboration remains absolutely vital.”
Charities and campaigners including the NSPCC and the Internet Watch Foundation (IWF) have also urged Meta to provide reassurances over the move.
Security minister Tom Tugendhat added: “The UK is proudly pro-privacy, pro-innovation and pro-security. We are also committed to protecting children online and ruthlessly pursuing those who seek to harm them.
“Our law enforcement agencies are working day and night to crack down on child sexual abusers.“The efforts of tech companies are crucial to their success. They have great influence over our lives, and with that power comes the responsibility to work with us to tackle this despicable abuse.”
Sir Peter Wanless, NSPCC chief executive, warned that offenders move children they have targeted on open platforms to encrypted services where they groom and ultimately abuse them.
“Tech firms should be showing industry leadership by listening to the public and investing in technology that protects both the safety and privacy rights of all users,” he said.
Ms Braverman on Tuesday visited a Kent Police investigation team dedicated to tackling online grooming.
Speaking afterwards, she said: “We’re facing a national and international crisis actually, whereby the scourge of online child sexual abuse is at prolific levels, where paedophiles are operating on groups hosted by Facebook or Instagram and they are abusing children”.
She added: “I’m ... calling on the tech companies, in particular Facebook, to embrace the technology so that we put child safety first and foremost.”
A Meta spokesperson said it has developed “robust safety measures” to combat abuse.
It added: “We’re today publishing an updated report setting out these measures, such as restricting people over 19 from messaging teens who don’t follow them and using technology to identify and take action against malicious behaviour.
“As we roll out end-to-end encryption, we expect to continue providing more reports to law enforcement than our peers due to our industry leading work on keeping people safe.”