Apple's iMessage and FaceTime also encrypt their data, and could fall under the ban along with other encrypted chat apps like Telegram.

The comments came as part of David Cameron's pledge to revive the “snoopers’ charter” to help security services spy on internet communications today.

He said: “In our country, do we want to allow a means of communication between people which […] we cannot read?” He made the connection between encrypted communications tools and letters and phone conversations, both of which can be read by security services in extreme situations and with a warrant from the home secretary.

But companies such as WhatsApp have remained committed to keeping their services encrypted and unable to be read by authorities, a project which has stepped up in the wake of the Edward Snowden’s revelations on NSA surveillance.

And privacy groups have repeatedly criticised attempts to limit the use of privacy tools in the name of security. When the government announced plans to crack down on the dark net, for example, but privacy groups have warned that much of the tools are used by people in oppressed countries and victims of crime to stay safe.