The Reform Government Surveillance group, formed in 2014 soon after the revelations of NSA surveillance by whistleblower Edward Snowden, said in a statement: "We have consistently raised concerns about proposals that would undermine encryption of devices and services by requiring so-called 'exceptional access' for law enforcement.
"Recent reports have described new proposals to engineer vulnerabilities into devices and services – but they appear to suffer from the same technical and design concerns that security researchers have identified for years. Weakening the security and privacy that encryption helps provide is not the answer."
The report referred to was an interview with former Microsoft employee Ray Ozzie in which he claimed to have found a way out for governments to bypass strong encryption without any backdoors.
The RGS group includes Microsoft, Apple, Google, Facebook, Dropbox, Twitter, LinkedIn, Oath: (the parent company of Verizon and Yahoo!) and Snap.
Some of these companies are said to have co-operated with the NSA in leaking consumer data, claims which they denied even though evidence was provided by Snowden to prove they had been willing partners.
This is the second time in a fortnight that the RGS has spoken up about encryption. On 24 April, the group issued a statement in which it acknowledged "that government leaders around the world are responsible for protecting the safety and security of their citizens, and that they increasingly seek to access electronic communications and data in their investigations".
But it added: "However, RGS respectfully disagrees with calls for legislation or regulations that would require companies to intentionally build security vulnerabilities into their products and services."
Governments around the world, including in Australia, have been calling for backdoors into encryption in order to tackle what are claimed to be unsolvable crimes.
In some cases, the claims of bodies like the FBI, that they could not gain access to devices in order to make progress in investigations, have been questioned and characterised as being somewhat overblown.