Braverman and Facebook clash over private message plans
Facebook's owner Meta has hit back at a government campaign strongly critical of its plans to encrypt messages.
Protecting messages with end-to-end encryption would mean that they could only be read by sender and recipient.
Home Secretary Suella Braverman said encryption could not come at the cost of children's safety, amid fears it can be used to conceal child abuse.
Meta argues that encryption protects users from invasion of privacy.
"We don't think people want us reading their private messages", the firm said.
"The overwhelming majority of Brits already rely on apps that use encryption to keep them safe from hackers, fraudsters, and criminals", it added.
Ms Braverman set out her concerns to Meta in a letter co-signed by technology experts, law enforcement, survivors, and leading child safety charities in July.
But on Wednesday she said: "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."
This is something Meta disputes. The BBC understands that the tech firm maintains it supplied that information in July. Much of the information it has is now published online.
Meta said that it had spent the last five years developing robust safety measures to prevent, detect and combat abuse while maintaining online security.
"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", it said.
But the plans mean hundreds of child abusers could escape punishment, according to the home secretary.
The National Crime Agency's (NCA) director of general threats, James Babbage, said if the platform introduces end-to-end encryption 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,"
At the time he blamed Mark Zuckerberg for the plan - criticizing what he called the "extraordinary moral choice" to expand encryption.
Meta - the American company of which Mr Zuckerberg is chief executive - has announced it will add end-to-end encryption, also known as E2EE, to all Facebook messenger chats, by default, by the end of the year.
The company already owns the encrypted messaging app WhatsApp. Other platforms such as Signal and Apple's iMessage also use encryption. All these platforms have criticized measures in the recently passed Online Safety Bill that might undermine the privacy of encrypted messages.
Meta writes: "When E2EE is the default, we will also use a variety of tools, including artificial intelligence, subject to applicable law, to proactively detect accounts engaged in malicious patterns of behavior instead of scanning private messages".
It also sets measures the firm takes to protect children, such as restricting people over 19 from messaging teens who don't follow them.
As part of its campaign against the move, the Home Office has joined the Internet Watch Foundation (IWF) to provide a guide for parents to "advise them how best to keep their children safe if Meta does implement end-to-end encryption".
It has also supported the production of a film against Meta's plans, which includes testimony from a survivor of child sexual exploitation online.
The IWF says its data shows the prevalence of the most severe forms of online child sexual abuse has more than doubled since 2020.