Animal rights activists say the cat is one of hundreds or possibly thousands of pedigree cats and dogs kept in pet shops in ways that defy international animal welfare standards.

One passer-by was so moved by Pai Chai's plight that she tried to buy her to find it a new home, but the shop owners were not interested.

Karen Tso said the owners told her Pai Chai was one of four breeding cats at the shop that were not for sale.

'The shopowner said Pai Chai is one of the shop's big treasures. But it sounded to me that the cat was a money-making machine,' Tso said.

The Society for Prevention of Cruelty to Animals said it planned to investigate the treatment of animals in pet shops, but the law at present gave inadequate protection.

'Long-term caging of animals does not constitute to an offence under the Prevention of Cruelty to Animals Ordinance, so unfortunately until our law is brought up to a level with most other developed countries [little can be done],' executive director Sandy Macalister said.

Veterinarian Dr Pauline Taylor said caging animals in isolation for long periods risked not only their physical health but also their mental state. 'For animals which have been kept in isolation for too long, their psychological problems are huge. It is not easy to rehabilitate them,' Taylor said.

Pet Trade Association president Howard Cheung Sin-ho said the shops did their best for their animals but Hong Kong's high rents and small shops made it difficult to give them more space.

'Most customers are animal lovers and they will assess how the shops treat their pets to decide if they will buy from them,' Cheung said.

The Food and Health Bureau said it would consult the Legislative Council in the middle of the year on ways to protect animal rights better.

It did not rule out any measures, including revoking the licences of animal traders found guilty of cruelty.

The Agriculture, Fisheries and Conservation Department said it already had the power to revoke traders' licences but had never done so.

It recorded seven prosecutions in 2009 and 18 last year for breaches of the Public Health (Animals & Birds) (Animal Traders) Regulations, which allow a maximum penalty of HK$1,000 fine for licence-holders and HK$2,000 for those who trade animals without a licence.

Law professor Amanda Whitfort of the University of Hong Kong said there would not be adequate protection for pets until the city had a law for animals requiring a reasonable welfare standard instead of a minimum legal level.

The practice of caging animals in small enclosures inside pet shops for long periods should be immediately addressed, Whitfort said.

'This is what our laws allow. The pet shops are only fulfilling the minimum legal requirements to keep the animal alive and to avoid prosecution,' Whitfort said.

The regulations require a living environment for animals that is dry and clean, with food and water, and enough space for the pet to 'move about freely and to stand, sit, lie and perch comfortably.'

The requirement for breeding animals is clearer, with a size of no less than two square metres for cats as sleeping and exercise areas combined.

For dogs, a sleeping area has to be no less than between 1.1 and 1.4 square metres, depending on the size of the dog. The legal requirement for an adjoining exercise area for dogs is more generous: no less than 3.7 square metres for small dogs, 5.5 square metres for medium-size dogs, and 7.4 square metres for large dogs.

However, some unscrupulous pet shops would simply keep the animal in the tiny 'sleeping areas' most of the time, so the law does not really help protect animal welfare.

'In many overseas countries like the UK, they have a requirement of giving animals a minimal standard of care, which means you can't leave an animal in a cage for its whole life.

'A minimal standard of care includes the right to enjoy natural behaviour, to socialise with other animal of its type, and to a suitable environment - a suitable environment is surely not a two-square-metre cage for its whole life.

'All these requirements are what a reasonable person would expect. We don't think leaving an animal in two square metres for 10 years is reasonable,' Whitfort said.

Some countries also impose time limits on the confinement and caging of animals, such as 21 days in South Australia and four weeks in Victoria in Australia.

Macalister said the SPCA would also like to see the animal welfare law have its present inadequate 'minimum' level raised to a standard that provided reasonable care and protection for animals.

'In the case of pet shops and breeders we would like to see this standard applied to more specific aspects. Cage size and construction is vital, but also including areas such as exercise, grooming, nutrition and veterinary treatment and checking.

'We would like to see a regulation that makes it mandatory at the point of sale that the pet shop has to provide the relevant information for any species containing such things as correct care, your legal obligations and the social obligations of owning that particular animal,' he said.

Taylor said animals confined in a small area for a long time would be vulnerable to joint disease and obesity. But the mental trauma to the animal was most difficult to cure.

'Normal behaviour is very important to any animal, like socialisation with other animals of its own kind. Animals also need some hiding place, soft, clean bedding, as well as space to stretch their legs,' she said. 'Cats should be given different levels to jump up and down.'

Whitfort added: 'I am not asking for something unfair like putting your cat on a cushion and then feeding it sardines. What I am asking is to let the animal have a normal standard of living, like an ability to exercise, play, hide and be mentally stimulated.'