They are the celebrity must-have gift of 2010, with Katie Price and Rupert Grint said to have fallen for the charms of the micro-pig, which sell for anything between £100 and £1,500.
But parents are urged not to buy the miniature porcine pets for Christmas, with the Government set to warn this week that they risk spreading dangerous diseases through family homes.
Ministers are so nervous about the craze, which has led to several owners being mis-sold regular piglets which grow into full-size sows, that guidance is to be rushed out next week specifically targeting prospective keepers of the pocket-sized creatures.
Animal Health, the government agency responsible for ensuring farm animals are healthy, disease-free and well looked after, will raise serious concerns about the hygiene threat posed by the animals. It will warn: "Before buying a pig, hobby keepers and owners of pet pigs or 'micro' pigs must make sure that they are aware of, and understand their obligations, so that they can keep their animals fit, healthy and legally compliant and help them to avoid unwittingly spreading disease."
Sick pigs can pass on zoonotic diseases to humans, which can include the skin condition erysipeloid and the bacterium Streptococcus suis, which can lead to illness including meningitis and deafness in humans. Simple actions such as washing hands and avoiding contact with animal excrement can prevent many infections, but the Government warns: "Parents and guardians should take into account the likely vulnerability of children to infection, and the difficulty in getting them to observe good hygiene practices, when deciding whether to keep any animal, including pigs."
Officials from the Department for Environment, Food and Rural Affairs are to raise their concerns about the keeping of micro-pigs as pets with the RSPCA at their next biannual working group.
Jim Paice, the farming minister, said: "This season, remember that a pig is a farm animal, and not a pet for Christmas. A micro-pig may sound like a popular gift idea – but beware the pig that grows too big. This year already I've heard some interesting stories about micro-pigs becoming bigger and outgrowing their homes. So if you'd like to see pigs this festive season, pop along to your local petting farm."
Keeping pigs as pets is not easy, with a web of paperwork aimed at the farming industry also covering hobby farmers. They require a lot of form filling, including obtaining a County Parish Holding Number before purchase, then obtaining a herd number and not moving the pig for three weeks to protect against disease. A movement licence is needed if the pig's location is to change. Most MPs, including Tory backbencher Mark Pritchard, have pressed the Government to demand that councils offer shelters for micro-pigs "abandoned by their owners".
Mr Pritchard said animal welfare was his main concern, with many families unaware of how to care for pigs properly. "A micro-pig is not a fashion accessory or a toy. It is a living animal, a sentient being."
Margaret Smith, 65, Ringwood, Hampshire
Mrs Smith bought what she thought was a micro-pig for her daughter Emma, 26. She has now started a Facebook page: "The Truth About Micro-pigs".
"We saw a micro-pig advertised: they were small, manageable and seemed ideal for the house and garden. We were told it grew no bigger than 14 inches, but at 18 months old he's now up to my waist. It's difficult to cope: we have an acre-long garden, but we've had to pen a third of it off for Pigwig. He yearned for company, so we had to buy another pig – a kunekune pig, which will stay small. We can't leave Pigwig alone or he'll wreck the place, so we have to babysit him constantly. We can't trust any animal that size with children."