While companies that export weapons are generally subjected to heavy government oversight, companies selling surveillance tools face no "global or national control," said the UN special rapporteur on freedom of opinion and expression, David Kaye.

In a new report presented to the UN Human Rights Council in Geneva, Kaye listed a range of products -- from computer intrusions to mobile device hacking tools -- that states can purchase to spy on opponents, journalists or activists.

He called the surveillance industry "a free-for-all", where companies effectively self-regulate in the absence of meaningful export controls.

He cited two companies that have published self-regulation policies, but argued that they only "gesture vaguely at the need to respect human rights".

The two companies are the Milan-based Hacking Team, which according to its website specialises in "offensive security", and the NSO Group, an Israel-based firm.

In an email to AFP, a NSO Group spokesperson said its technology "helps prevent terrorist attacks, stop drug and sex trafficking rings, and rescue kidnapped children, but it is not a tool to be weaponised against human rights activists or political dissidents.

"That's why there is such a high bar for ever becoming a licensed customer," the spokesperson said.

Its independent "ethics Committee", which includes security, intelligence and geopolitical experts, "can block sales to potential customers without regard to commercial interests", the spokesperson added.

Hacking Team did not immediately reply to a request for comment.

- 'Immediately cease' sales -

Kaye noted in the report that developing an international, rights-based framework to govern the production and export of surveillance technologies would take time.

"In the meantime, scores of journalists, activists, human rights defenders and government critics will be at the mercy of governments emboldened by the array of highly intrusive surveillance tools at their disposal," he added.

Until adequate rules are in place, Kaye argued that companies should "immediately cease the sale and transfer", of such technologies until they have satisfied specific criteria demonstrating that none of their products support rights violations.

United Nations special rapporteurs are independent experts who do not speak for the world body, but report their findings to it.