Avon and Somerset police are training an extra 150 officers to use electric stun guns, bringing the total to 300.

Currently, there are 120 firearms officers and 30 others who carry Tasers, but a further 150 officers will now carry the 50,000-volt stun gun.

The force was involved in a year-long pilot study to establish how useful the weapon was in defusing potentially violent situations.

The trial started in September 2007 when the force initially trained 30 Support Group officers.

They found that where Tasers were present it contributed to the quick and safe resolution of incidents.

More officers will be trained throughout 2009.

The first 60 will be in the Somerset area after a review highlighted the need for increased capability to respond to violent incidents in more remote areas of the force.

About 50 officers from the Road Policing Unit and 30 officers from the Support Group will also have training phased in over the year.

This will bring the total number of Taser-trained officers to 300 across Avon and Somerset, though they will have to share 200 of the stun guns between them.

Somerset West chief inspector Yan Georgiou said: "The number of officers being assaulted or injured on duty is reducing. There are many reasons for this, but there is no doubt that Taser is a contributory factor."

Somerset East chief inspector Paul Richards said: "Tasers have proved a useful tactical option for officers faced with threats of violence of such severity that they would need to use force to protect the public, themselves or the offender. In many cases, the presence alone of a Taser can act as a deterrent to offenders, and so it is hoped that many future situations will be resolved without conflict."

A Taser works by firing two barbs which penetrate the skin and discharge 50,000 volts along two copper wires attached to the gun. It can also be held against a person and fired to temporarily incapacitate. Despite the high voltage, a Taser bolt is considered safe because of its low amperage. Police say it has no side effects and can even be used on people who have a pacemaker.

As part of a Government package, more than 6,000 officers across the country are being trained to use Tasers.