WhatsApp has lead calls for the UK government to rethink its Online Safety Bill, as it reaffirms its commitment to privacy.

Over-the-top messaging services have long advocated the use of end-to-end encryption, with WhatsApp famously seeing it as a central tenet of its whole business model. However, the company has joined others to warn that measures included within the latest Online Safety Bill could lessen the protection their services offer users, by providing governments a ‘back door’ to read otherwise private communications.

End-to-end encryption means that only the sender and recipient of a message are able to read it – even WhatsApp itself cannot access message content.

The government has said that it supports encryption methods, but not if they’re being used to protect terrorists, child abusers or other lawbreakers. It has called for greater transparency in the interest of public safety, saying tech companies have a “moral duty” to root out illegal activities being carried out on their platforms.

In response, a whole host of messaging platforms have decried the Online Safety Bill, arguing that it opens the door to “routine, general and indiscriminate surveillance”.

Various CEOs, presidents and directors from WhatsApp, Signal, Wire, Element, Threema, Viber and Oxen Privacy Tech Foundation signed the open letter, which warned that “weakening encryption, undermining privacy and introducing the mass surveillance of people’s private communications is not the way forward.”

They went on to rubbish claims by the government that ways of scanning messages without undermining end-to-end encryption could be found. “The truth is,” they wrote, “this is not possible.”

As well as a warning the letter came with a real threat, with signatories saying they would sooner abandon the UK market altogether than dilute their security practices. WhatsApp told the BBC it would choose leaving the UK over changing its encryption, whilst Signal put the likelihood of it withdrawing should these measures pass at “100%”.

Others have argued that weaker encryption technologies could put British national security at risk. Such back-door entries to otherwise private messages may not just be open to the state or tech platforms, but could be accessed by hackers, who would then be granted access to a tranche of valuable data that would otherwise not have been open to them.

Parliamentary debates around the Online Safety Bill and how it would be applied are ongoing.