However, they can now be used against all potentially violent offenders even if they are unarmed.

It is the decision not to ban their use against minors that is likely to raise serious concerns.

Home Office Police Minister Tony McNulty said medical assessments had confirmed the risk of death or serious injury from Tasers was "low".

But he failed to mention Government advisers had also warned of a potential risk to children.

The Defence Scientific Advisory Council medical committee told the Home Office that not enough was known about the health risks of using the weapons against children.

Tasers work by firing metal barbs into the skin which then discharge an electrical charge which is designed to disable someone long enough to allow police to detain them safely.

The committee, which is made up of independent scientists and doctors, said that limited research suggested there was a risk children could suffer "a serious cardiac event".

It recommended that officers should be "particularly vigilant" for any Taser-induced adverse response and said guidance should be amended to "identify children and adults of small stature" as being at potentially greater risk from the cardiac effects of Tasers.

The Government scientists were also asked to test whether the weapons could cause a miscarriage if used on a pregnant woman.

While not saying whether police would be allowed to Taser an expectant mother, the Home Office said the DSAC committee had "specifically asked" for computer simulations to be carried out to analyse the effect on "a pregnant female".

Amnesty International claims Tasers have been responsible for 220 deaths in America since 2001. Many cities and police forces there have banned their use against minors.

Two years ago in Chicago a 14-year-old boy went into cardiac arrest after being shot with one. Medics had to use a defibrillator four times to resuscitate him.

Taser International, the American firm that makes the device, said tests on pigs suggested the weapons were safe.

The Association of Chief Police Officers, which issues guidance to forces on the use of weapons, said Tasers would be made "readily available" for "conflict management" at incidents of "violence and threats of violence of such severity that they will need force".

Non-firearms officers in ten forces will be trained to use the weapons. Every incident they are involved in will be assessed over a 12-month trial period.