They are the first into dangerous situations and more likely than any police officer to find themselves staring down the barrel of a gun.

But Sussex's police dogs will get greater protection in the line of duty if trials of bulletproof vests are successful.

The force is one of the first in the country to trial the body armour, a common sight within American police departments.

The vests, on loan from the USA manufacturers, are being worn by firearms support dogs, trained to assist the force's Special Operations Unit on firearms incidents. All five Sussex Police firearms support dogs, German shepherds named Boss, Oban, Rodney, Razz and Ben, have tried on the vests for brief training sessions.

Pete Sims, dog unit co-ordinator, said: "They wriggled at first to say, 'What's that on my back?' but after that they went through their paces as normal.

"The armour is surprisingly light and none of the dogs seemed to mind wearing it."

The armour is made by Second Chance Body Armour, a Michigan-based company with a branch in Scotland.

Sussex Police safety staff were studying the company's catalogue for vests for officers when they spotted the dog version.

Mr Sims said the dogs' welfare was paramount. No Sussex dog has ever been shot but other forces in Britain have suffered fatalities.

Mr Sims said: "The vest clearly doesn't cover the entire dog but it protects his vital organs, liver, kidneys and heart. It improves the dog's chances of survival by 80 per cent."

Mr Sims, a police dog handler for 27 years, said: "I have gone into situations in the past wearing body armour. The poor dog goes in first to check whether anyone is there and he's not wearing any protective gear.

"The idea behind the vests is simple - we don't want to risk losing them."

He said the vests will provide a little extra warmth for the dogs in winter, but could prove hot at the height of summer. He said: "But they usually only wear them for an hour at any one time and, in any case, I don't think we need worry too much about excessively hot weather in this country."

If the trial proves successful, three of the £300 vests will be bought.

Inspector Dave Hart, of the dog unit said: "Our dogs are very valuable to us. I am hoping the trial will enable us to give them added protection whilst allowing them to do the job they are specially trained for."