The following letter was published in the Guardian on Friday 10 July, 2015, from representatives of three leading human rights organisations, who have called on the prime minister David Cameron to launch an inquiry into why the intelligence services spied illegally on Amnesty International.

The revelation that GCHQ has been monitoring its communications came in a revised judgment this month from the Investigatory Powers Tribunal (IPT), the body responsible for handling complaints about state surveillance:

One measure of a free society is how it treats its NGOs and campaign organisations. The recent revelation (Rights groups targeted by GCHQ spies, 23 June) that Amnesty International has been snooped on by the UK security services is the death of the canary in the coalmine.

Ever since whistleblower Edward Snowden revealed the existence and scale of the US and UK mass surveillance programmes two years ago, campaign groups across the world have been worried that we are being spied on. We now know definitively that Amnesty International and the Legal Resources Centre in South Africa were. That is likely to be just the tip of the iceberg.

We only know what little we do because GCHQ fell foul of its own internal rules on handling communications once they had been intercepted.

As human rights organisations, we all work regularly with victims of abuses and government critics. That vital work is put in jeopardy if people can justifiably fear that their confidential communications with us might be opened up by governments.

Many questions remain. Which other organisations are being spied on? What confidential information was GCHQ looking at? Why was it of interest? Who read it? Was it shared? Is it still going on? How did it come to this?

David Cameron must immediately set up an independent inquiry into how spying on law-abiding human rights organisations was allowed to happen, and what justification there could possibly be for such an invasive and chilling violation of privacy.

Kate Allen, UK director, Amnesty International
Shami Chakrabarti, Director, Liberty
Gus Hosein, Executive director, Privacy International

• Any plan to bypass or ban end-to-end encryption will only be of limited help in spying on terrorists. Though only the new permitted encryption schemes would be used in officially available apps, the fact that working encryption standards are open source and available means that anyone determined enough could program their own applications which use them. Terrorists are known to adapt their methods quickly, the public is not. I wonder why the spy masters and government are so determined to push through such legislation.

Mustafa Aydin,
Department of computer science, University of York.

In a separate letter sent by Amnesty to Cameron, the human rights group asks for an urgent meeting with the prime minister and for “as much as possible” of the IPT’s secret findings to be published.

Kate Allen, Amnesty UK’s director, said:

It’s absolutely shocking that Amnesty International’s private correspondence was deemed fair game for UK spooks, who have clearly lost all sense of what is proportionate or appropriate.

A key measure of a free society is how it treats its charities and NGOs. Snooping on charities is a practice straight out of the KGB handbook. If Amnesty International is being spied on, then is anyone safe?

Downing Street said it was considering its response to Amnesty International’s letter, repeating the government statement given at the time of the IPT judgment:

The IPT has confirmed that any interception by GCHQ in these cases was undertaken lawfully and proportionately, however technical errors were identified.

GCHQ takes procedure very seriously. It is working to rectify the technical errors identified by this case and constantly reviews its processes to identify and make improvements.”

Satellite receiver dishes at a GCHQ facility near Bude, Cornwall.

“Snooping on charities is a practice straight out of the KGB handbook.”

And I thought the Tories were claiming to be minarchist types, with state shrinking aims …

Photograph: Education Images/UIG/Getty.