If a new law undermined encryption, the encrypted messaging app Signal has threatened to stop operating in the UK.
According to Signal president Meredith Whittaker, the organization "would absolutely, 100% walk" if required to compromise the privacy of its messaging system by the Online Safety Bill.
The government claimed that its suggestion did not "ban end-to-end encryption.".
Parliament is currently debating the Boris Johnson-introduced bill.
According to critics, the new law may mandate that companies scan messages on encrypted apps for references to child sex abuse or terrorism.
Businesses that facilitate private, secure communication have been concerned by this.
The BBC was informed by Element, a UK business whose clients include the Ministry of Defense, that the plan would cost them business.
WhatsApp previously assured the BBC that it would not compromise security for any government.
The government and well-known child protection organizations have long argued that encryption undermines efforts to stop online child abuse, which they claim is an issue that is getting worse.
The Home Office said in a statement that "it is important that technology companies take all reasonable steps to prevent their platforms from serving as a breeding ground for pedophiles.".
The statement continued, "The Online Safety Bill does not represent a prohibition on end-to-end encryption but makes clear that technological advancements should not be made in a way that compromises public safety, especially children's online safety.
"We can and must have both privacy and child safety; it is not a choice. ".
To believe that we can have privacy, though, "but only for the good guys," according to Ms. Whittaker, is "magical thinking," she told the BBC.
"Encryption is either protecting everyone or it is broken for everybody," she continued. ".
A subset of this magical thinking, according to her, is "embodied" in the Online Safety Bill.
On the Google Play store alone, Signal has received over 100 million app downloads.
It employs end-to-end encryption, a method that encrypts messages so thoroughly that not even the company running the service can decipher them.
Journalists, activists, and politicians use the app, which is run by a non-profit organization with a Californian base.
Along with Facebook and Telegram, which are optional, WhatsApp also uses end-to-end encryption.
Following criticism, Apple dropped plans to implement a system in which messages sent from phones and other devices would first be encrypted before being checked for images of child abuse.
Some have suggested that tech companies may have to use this strategy, known as client-side scanning, but detractors claim it effectively defeats the purpose of encryption.
According to Ms. Whittaker, it would effectively transform everyone's phone into a "mass surveillance device that phones home to tech corporations, governments, and private entities.".
"Back doors" that allow for the scanning of private messages would be exploited by "malignant state actors," according to Ms. Whittaker, and "create a way for criminals to access these systems.".
When asked if the Online Safety Bill might endanger their ability to provide a service in the UK, she told the BBC: "It might, and we would absolutely, 100% walk rather than ever undermine the trust that people place in us to provide a truly private means of communication.
"We have never compromised on our privacy commitments, and we never will. ".
The threat of mandatory scanning, alone, would cost him clients, according to Matthew Hodgson, chief executive of Element, a British secure communications company.
Customers, he claimed, would assume that any secure communication device made in the UK would "necessarily have to have backdoors in order to allow for illegal content to be scanned.".
Additionally, it might lead to "a very surreal situation" where a government bill might erode security assurances provided to clients at the MoD and other delicate areas of government, the speaker continued.
The business might have to stop providing some services, he added.
Everyone wants to protect children, Ms. Whittaker said, adding that some of the stories that are cited are gruesome. ".
When asked how she would respond to claims that encryption shields abusers, Ms. Whittaker said she believed that most abuse occurred in the family and in the community, where she argued the focus of efforts to stop it should be. .
She cited a paper by Professor Ross Anderson in which he called for increased funding for child protection services and cautioned that "the idea that complex social problems are amenable to cheap technical solutions is the siren song of the software salesman."
