Last week Apple announced a range of new features designed to protect children, including protection from sensitive images in iMessage and iCloud photo scanning for child sex abuse material (CSAM).
But prominent privacy advocates have criticised the technology giant's move as the eroding of privacy, with the Electronic Frontier Foundation (EFF) branding it "a backdoor into its data storage system and its messaging system".
The system works by comparing a digital fingerprint - known as a hash - of an image uploaded to iCloud and comparing it to a database of known hashes of CSAM images.
Another aspect involves warning parents if their child under 13 years old sends or views photos containing sexually explicit content.
"We've said it before, and we'll say it again now: it's impossible to build a client-side scanning system that can only be used for sexually explicit images sent or received by children," India McKinney and Erica Portnoy of the EFF wrote.
"As a consequence, even a well-intentioned effort to build such a system will break key promises of the messenger's encryption itself and open the door to broader abuses.
"Apple should make the right decision: keep these backdoors off of users' devices."
WhatsApp head Will Cathcart was equally scathing.
"People have asked if we'll adopt this system for WhatApp. The answer is no," he wrote in the first of a series of tweets.
"Apple has built software that can scan all the private photos on your phone - even photos you haven't shared with anyone. That's not privacy.
"We've had personal computers for decades and there has never been a mandate to scan the private content of all desktops, laptops or phones globally for unlawful content. It's not how technology built in free countries works."
In an internal memo reported by 9to5 Mac, Sebastien Marineau-Mes - a software VP at Apple - acknowledged there had been concerns raised but said the tools protected children and maintained "Apple's deep commitment to user privacy".
"We know some people have misunderstandings and more than a few are worried about the implications, but we will continue to explain and detail the features so people understand what we've built," he wrote.
But that hasn't placated everyone - 31 organisations and over 5500 individuals have signed an open letter to Apple demanding it stop the deployment immediately and re-affirms its commitment to privacy and encryption.
The systems will initially be launched in the US with plans to expand the service based on the laws of each country where Apple operates, the company said.
