Taser stun guns used by police are potentially deadly and must be strictly controlled, a leading human rights group has warned.
Taser guns fire needle-tipped darts up to 21ft to disable suspects
Amnesty International says the
high-voltage weapons have been linked to more than 70 deaths in America.
It wants assurances from the Home Office and UK police chiefs that Tasers will only be used in extreme cases.
The home secretary says Taser guns carry a very low risk of fatality, much lower than conventional firearms.
In September, David Blunkett authorised their use by police firearms officers across England and Wales, following a successful year-long trial.
But Amnesty says the guns should be treated as "potentially lethal weapons" and be subject to the same restrictions as conventional firearms.
It says the guns should only be used by trained firearms officers to prevent the loss of life or serious injury.
But a Home Office spokesman said this was already the case with Tasers which were only available for use by specially trained officers where the authority to use firearms had already been granted.
Amnesty International UK Director Kate Allen said: "Tasers have been used in the US against pregnant women, unruly schoolchildren and mentally ill people.
"In some cases, simply walking away from a police officer has led to people getting a 50,000 volt electric shock.
"Is this a glimpse into the future of UK policing?"
Amnesty is also calling for a "rigorous, independent and impartial study" into the use and effects of the Tasers.
It warns they cause "intolerable pain" and are "inherently open to abuse".
Amnesty say many experts believe Taser shocks "may exacerbate the risk of heart failure" in people under the influence of drugs or with some health problems.
A Home Office spokesman said that only authorised firearms officers were permitted to use Tasers and that they had to follow guidelines set by the Association of Chief Police Officers (Acpo).
He said: "Police officers need to be equipped to deal with dangerous situations where they have to protect themselves and the public."
But he stressed that the risks of the options open to officers to do that had all been carefully considered. "Any use of force will carry some risk of physical injury," he said.
"Independent medical research shows, however, that the risk of death from Tasers is low, and certainly very much lower than that from conventional firearms.
"We continue to research the health implications using Tasers, and continue to develop the use of this and other lethal options."
The devices, which can fire up to 21ft to disable suspects, were trialled by police in the Metropolitan force, Northamptonshire, Lincolnshire, Thames Valley and North Wales.
Acpo had welcomed the extension of their use, saying the weapon had been shown to have a significant deterrent effect.
During the trial, the guns were deployed in 60 incidents and aimed in 40 of those, but actually fired only 13 times.
They were trialled after growing pressure for a less lethal weapon in a bid to reduce the number of people shot dead by armed police.
The Independent Police Complaints Commission (IPCC) said it shared Amnesty's concerns and accepted there were "inherent dangers" in their use.
Chairman of the IPCC Nick Hardwick, said: "The IPCC supports the use of Tasers as less lethal options for trained firearms officers only.
"If the option is to shoot somebody dead or use a Taser, we back the use of the Taser every time."
However, he said during the year-long trials nobody suffered any serious injuries.
He said police officers are "fully accountable for the actions" because the IPCC is informed when Tasers are fired and the guns record when they are used.
"Already it has definitely saved lives in this country and probably saved serious injury to officers as well, " he said.