The United Nations Convention Against Torture has linked the taser stun-gun to torture, one month before a report on the weapon is due out from the New Zealand Police.
"The use of these weapons causes acute pain, constituting a form of torture," the UN committee concluded.
The committee said studies have been carried out overseas showing the taser was dangerous and can cause death.
The comments are included in the committee's thirty-ninth report and come two weeks after unarmed Polish immigrant Robert Dziekanski died in a taser related incident.
In a graphic YouTube video, Mr Dziekanski was shown to be shot by police using stun guns at an airport in Canada.
His death has sparked a review of the weapon's use in Canada.
A year-long test of the tasers in New Zealand ended in August.
Police fired the taser 20 times during the trial. Police also withdrew the gun over 120 times.
The trial included officers in the Auckland, Waitemata, Counties Manukau and Wellington districts.
A report on the pilot is expected next month, with a decision on their long-term to be made in January.
In a written statement, police spokesman Jon Neilson told nzherald.co.nz the evaluation will consider "relevant" overseas reports but he did not make mention of the UN report directly.
"We have been keeping a close watch on the deployment of the taser in the UK and the reports that have emanated during their trials and implementation," Mr Neilson said.
But barrister and spokeswoman for the Campaign Against The Taser, Marie Dyhrberg, said the UN report cannot be rejected, given the UN's reputation for independence and expertise.
She said she has concerns that the police may not take this report and others into account when evaluating the taser.
"The police seem to be on a course that the taser will come in irrespective," Ms Dyhrberg said.
She said the taser has been billed as a last resort to lethal weapons but that standard has been eroded in New Zealand and the rest of the world.
"One firing is bad enough but we see repeated firings and we see the effects of it," she said.