The mobile-messaging application WhatsApp and the Facebook app are displayed along with other apps on an Apple iPhone.

Tech giants, civil society groups and Ivy League security experts have condemned a proposal from Britain's eavesdropping agency as a "serious threat" to digital security and fundamental human rights.

In an open letter to GCHQ (Government Communications Headquarters), 47 signatories including Apple, Google and WhatsApp have jointly urged the U.K. cybersecurity agency to abandon its plans for a so-called "ghost protocol."

It comes after intelligence officials at GCHQ proposed a way in which they believed law enforcement could access end-to-end encrypted communications without undermining the privacy, security or confidence of other users.

Details of the initiative were first published in an essay by two of the U.K.'s highest cybersecurity officials in November 2018. Ian Levy, the technical director of Britain's National Cyber Security Centre, and Crispin Robinson, GCHQ's head of cryptanalysis (the technical term for codebreaking), put forward a process that would attempt to avoid breaking encryption.

The pair said it would be "relatively easy for a service provider to silently add a law enforcement participant to a group chat or call."

In practice, the proposal suggests a technique which would require encrypted messaging services — such as WhatsApp — to direct a message to a third recipient, at the same time as sending it to its intended user.

Levy and Robinson argued the proposal would be "no more intrusive than the virtual crocodile clips" which are currently used in wiretaps of non-encrypted communications. This refers to the use of chat and call apps that can silently copy call data during digital exchanges.

Opposing this plan, signatories of the open letter argued that "to achieve this result, their proposal requires two changes to systems that would seriously undermine user security and trust."