Assembly Members may be under surveillance by a UK spy agency, according to human rights organisation Amnesty International.
Amnesty International has written to all MLAs warning them that their communications could be under surveillance by electronic eavesdroppers at GCHQ.
The move follows reports that GCHQ is no longer applying the so-called Wilson doctrine to members of devolved assemblies in the UK.
The Wilson doctrine, named after former Prime Minister Harold Wilson, protects MPs' phones and electronic communications.
GCHQ has previously also applied it to the communications of MLAs and MEPs. However, recent reports suggest that this is now no longer the case following a change in policy by the spy agency.
The policy change now means that members of devolved administrations and MEPs no longer have these protections. The guidelines in place before March stated: "As a matter of policy GCHQ applies the principles of the Wilson doctrine to Members of the House of Commons, Members of the House of Lords, UK MEPs, and members of the Scottish, Welsh and Northern Irish assemblies."
The new guidelines state: "The doctrine does not apply to... the interception of communications of Members of the European Parliament or devolved assemblies."
SDLP MLA Alex Attwood said Members of the Assembly must be off-limits to GCHQ "as should members of all devolved assemblies". Mr Attwood said: "Our democracy has been hard won and cannot be vulnerable to the unaccountable reach of GCHQ."
Amnesty NI director Patrick Corrigan said: "The change in GCHQ's interpretation of the Wilson doctrine illustrates why mass surveillance is so damaging to a free society. If our elected representatives are not safe from the spies, who is? For the rules on spying on elected representatives across the UK to change without any sort of public scrutiny or accountability, is outrageous. We need to know from the Northern Ireland Executive what - if anything - they knew about this change.
"Amnesty International fought through 18 months of litigation at the Investigatory Powers Tribunal and a wall of denials to get confirmation that we were also subject to mass surveillance by the UK Government via GCHQ."