Hills Pet Nutrition is a company that walks the talk - and the dog too. At the company's site in Hertfordshire in Britain, several dogs can often be found in the office.

"We are a company of pet lovers. It is encouraged by the business and enshrined in the mission statement," says veterinary affairs manager Libby Sheridan, adding that there is nothing like walking her dog Gulliver at lunchtime to blow the mental cobwebs away.

As Hills is a maker of pet products, this might be expected. But the Los Angeles-based advertising agency TBWA\Chiat\Day takes a similarly pro-canine line.

There may be 40 to 50 dogs - compared with 850 people - in the company's largest office at any time, says Jeremy Miller, director of public relations. "It has been going since 1998. It started with the company's chairman and chief officer, who's a dog lover. It creates a good environment."

The only downside, he says, is "the occasional scuffle".

For many employees, the presence of the family pet at work is a big perk, making them more relaxed and keeping them in good spirits. They may even work longer hours if they know the dog is under the desk. "If it is practical it can be a great benefit," says Ziela Haider, a spokeswoman for the Blue Cross, an animal welfare charity. "Dogs really do reduce stress. We have a part-time office dog and spending a few minutes stroking him lets you take a mental break."

The nation that has truly embraced pets at work is the US. According to a survey by the American Pet Products Manufacturers' Association, nearly one in five companies allows pets in the workplace.

Of course, there have to be rules for those who want to let the dogs in. The animals must be well behaved (with appropriate sanctions if they are not); they should not affect employees who do not like or get on with pets; the policy needs agreement by consensus; and there must be iron-clad rules about cleaning up.

Cary Cooper, professor of organisational psychology and health at Lancaster University management school, says inviting pets into the workplace could reduce stress and make the company a more fun place to be.

He also believes pets humanise colleagues: "People step out of the corporate roles they play with animals. You no longer think 'Fred's my manager', you think 'Fred loves his dog'."

However, Steven Welch, associate director at the Hay Group, a human resources consultancy, is concerned about the possibility of distraction, not to mention allergies and legal liability.

"You could make a work-life balance argument for it, but businesses are places of work - they are not a zoo and they are not show-and-tell. If you want to do better on work-life balance, let your employees do more work from home, so they can be with their pets."

The pets-at-work debate almost always revolves around dogs, but if companies really want to mix things up, they can always get pet-friendly with more exotic fauna.

In April, a metre-long ball python called Kaiser escaped from his cage at pet-friendly Google's New York offices. According to the company's official blog, after consulting a herpetology expert at the American Museum of Natural History, the errant snake was found relaxing behind a filing cabinet.

Kaiser is now back at his owner's home - where he'll be staying.