Yigal Chazan reports on the controversial dog training methods

The calls come after three policemen were found guilty of mistreating their police dogs on Thursday.

Chelmsford Magistrates Court convicted one sergeant and two constables from the Essex police dog centre of a number of offences under the Protection of Animals Act.

The trial was told that the dogs' choke chains were used to hang them from fences and posts as they were beaten.

The UK's largest dog welfare group - the National Canine Defence League (NCDL) - is calling on the government to control use of training devices such as collars with sharp spikes.

These devices are widely available from animal interest magazines or many pet shops.

The NCDL's Colette Case says there is now a strong case for regulation.

"You can phone up and hire an electric shock collar to give your dog electric shocks by the week. It's very very accessible."

Ms Case said she hoped the Home Office would be reviewing all dog training methods and that this would be one area that it will consider.

"We certainly would urge them to look at the sort of equipment that they're using and the risks of damage - both psychologically and physically - to the animals by using them incorrectly," she said.

Long-term harm

Another animal welfare group, the RSPCA, stresses that these training devices can be harmful.

"The electronic devices can actually burn the skin and cause long-term problems to the skin. Some of the pinch collars produce bruising, ulceration and actually cuts to the skin in exteme circumstances," said its Assistant Chief Veterinary Officer, Chris Lawrence.

Welfare groups are also concerned about a more widely used form of training aid - the choke or "check" collar - a type of noose which is tightened around the dog's neck when it misbehaves.

Robin Walker of the British Small Animal Veterinary Association (BSAVA) says it has often been misused over the years and causes dogs severe injuries.

He says that vets have seen injuries such as severely sprained necks, dislocated neck bones, haemhorrages into the eyeballs, crushed windpipes and paralysed larynxes.

The BSAVA cautions that training aids which inflict some degree of physical pain on a pet should only be used as a last resort, and then only after consultation with a vet.

The BSAVA - along with other welfare groups - believes that "positive reinforcement" methods which reward dogs for good behaviour should always be used in the first instance as the preferred method of improving discipline.