More and more British pets are being given Prozac to help them battle against depression.

Tropical birds such as parrots are the worst affected, according to television vet Romain Pizzi.

Mr Pizzi, a specialist in zoo and wildlife medicine for the Royal College of Veterinary Surgeons, says pets are affected when owners leave them alone for hours on end.

He told the Daily Telegraph: "Contrary to some people's expectations parrots are very intelligent and sensitive animals.

"Typically if people go out to work all day their parrot will get very bored and frustrated and eventually develop depression."

Mr Pizzi, the director of Edinburgh-based consultancy Zoological Medicine, said Prozac was only prescribed in "the most extreme cases".

"It doesn't cure all animals, but around two-thirds respond to the treatment. In a small number of cases things will go well until we wean them off Prozac and the problems return," he said.

"Unfortunately there is a big proportion of people who buy these birds because they are pretty and they talk. They are not thinking it through in terms of their lifestyle. Parrots require a lot of care and stimulation."

Birds are not the only pets that get depressed - recent research suggested that as many as 632,000 cats and dogs in the UK area affected.

Vet and small animal specialist Mark Johnston said: "A dog can't sit on the couch and discuss his worries but he can howl the house down, chase his tail or chew everything to pieces."