The weapons fire a 50,000-volt electrical charge for five seconds

The forces will be able to use Tasers - US-made, hand-held electric stun guns - from Wednesday.

Only specially-trained and authorised firearms officers will be allowed to use the weapon, which can be used instead of conventional firearms.

The Taser guns, pioneered in America in the 1970s, deliver a five-second 50,000 volt charge.

Head of Operations at Lancashire Constabulary, Ass Ch Con Julia Hodson, said: "The police service is constantly seeking less than lethal options to resolve dangerous situations safely and without injury.

"The Taser provides officers with another tool that may be more appropriate than a conventional firearm in certain circumstances.

Tests have shown that the Taser is very effective while the charge is being applied Ass Ch Con Mick Giannasi Merseyside Police

"It reduces the risk to officers, offenders and members of the public because it can be fired from a distance and is an alternative to a firearm.

"It is a strong visual deterrent that does not cause serious injury and has no lasting physical effects."

In September 2004, the Home Office announced that all firearms officers in England and Wales would be allowed to use the Taser.

Mr Mick Giannasi, of Merseyside Police, said: "The Taser, along with the plastic baton round, is a less lethal option and in no way replaces the conventional firearm.

"Armed response teams will now have the option to use Tasers as part of a range of equipment to diffuse a difficult situation and tests have shown that the Taser is very effective while the charge is being applied."