Primate owner Laura was scanning the internet adverts for monkeys she could try to rescue when she spotted one from a man in the Cotswolds who was clearly finding caring for two common marmosets extremely difficult. This is a common problem: primates are wild animals and keeping them is complex, expensive and demanding.

She contacted the man and agreed to collect the two adult monkeys – one male and one female. They had been kept in a tiny shed in his garden and were in a terrible condition. “He’d fed them almost entirely on porridge, baby food and fish fingers. When I asked if he had given them any fruit or vegetables, he remembered that he’d occasionally fed them grapes. Neither monkey had ever been seen by a vet. The male had severe dental problems and his tail was a mixture of matted hair and bald patches.”

Like many of us, Laura (not her real name) grew up fascinated and enthralled by monkeys, and although she had never intended to keep primates, she found herself rescuing the two marmosets. She soon realised that the female was pregnant and, two weeks later, twin males were born. Soon after, the adult male was booked in for surgery to fix his tail and teeth. While the marmoset was under anaesthetic, the vet discovered that his tiny body was riddled with metabolic bone disease caused by poor nutrition and insufficient light. Sadly the male died during the operation – though, with his twisted bones and body bloated by gas, it seemed a slight blessing when his heart finally stopped.

A common marmoset in the Atlantic rainforest, Brazil. Photograph: Alamy

This sad story doesn’t stop there. Before he died, he’d managed to get the female pregnant again – and soon another three tiny males were born. Laura then rescued another adult male (this time from Luton), and what had started out as a single pair now turned into a family of seven – with the new male acting as a surrogate father.

They all now live in at her family home in Lincolnshire in a specially made enclosure with specialist heating, specific lighting, indoor and outdoor runs and an ever-changing regime of feeding and behavioural enrichment. A contraceptive implant has ensured no more little monkeys have since arrived on the scene and now, finally, both the monkeys and keeper are happy.

But Laura admits that primates make awful pets: “They urinate on everything to mark their territory and smell terribly; they need constant care and easily cost thousands of pounds every year to keep. People have this idea that they can touch and cuddle them but I never touch mine as they’re not tame. If I did, I’d expect to be bitten. Even with my most relaxed animal, I wouldn’t dream of it as it would stress him out too much. It’s such a selfish thing to have them as pets. Get a dog or have a baby – just don’t get a monkey!”

Welcome to the world of primate ownership: the legal position is complex, the ethics troublesome, and even the owners themselves have conflicted feelings about keeping monkeys at home. I’d tried contacting several other primate owners but, with this one exception, none would speak to me. I got a sense that they knew it was wrong at some level and were uncomfortable talking about it.

I am a primatologist and have worked with chimpanzees in Africa, orangutans in Indonesia and green monkeys in the Caribbean. I love primates and have dedicated years to working with them, but there is not a chance I would want one as a pet.

Squirrel monkeys are on the dangerous animals list. Photograph: Alamy

But there are people who want to – an estimated 4,500 primates (which covers apes, monkeys and lemurs, bushbabies and lorises) are privately owned in the UK. While some of these are owned by trained experts and represent specialist breeding groups, the vast majority are pets, living in people’s homes. Often owned by individuals with nothing more than good intentions and the misguided desire to own a “cool” pet, it is clear that there are very few privately owned captive primates in the UK in such a lucky situation as the ones Laura rescued.

Dr Sharon Redrobe – a veterinary surgeon and the CEO of Twycross Zoo, Warwicks – knows first-hand just how hard primate husbandry is. “By definition, a pet is an animal we touch and play with in our homes and in no way is it in a primate’s best interest to be constantly touched and played with by people. They need their own social groups, are extremely hard to care for and often grow up to be aggressive and impossible to control. Owners then take them to a vet, expecting them to be magically ‘fixed’. They’re wild animals and, in that respect, no different to tigers. You wouldn’t keep a tiger at home, so don’t keep a monkey.”

Redrobe is quick to point out that in the past keeping pet primates was far more socially acceptable and that places such as Twycross were actually founded by people who liked to keep pet monkeys themselves, but she says times have moved on.

“The world has changed hugely since the 1950s and 60s. We didn’t know any better then; now we do. If you really love monkeys, let them be monkeys. Maybe help them by sponsoring one in a zoo or sanctuary.”

Despite such complicated care needs, high welfare concerns and the serious risks associated with the spread of certain diseases between people and non-human primates, it is still legal to keep primates as pets in the UK – regardless of how endangered they are or how dangerous they may be.

The care of primates is covered by the Animal Welfare Act of 2006 and Defra’s Code of Practice for the Welfare of Privately Kept Primates (the “primate code”) of 2010. The act, which states that animal owners must prevent “unnecessary suffering” and must take “all reasonable steps to meet their animal’s needs”, is hard to enforce as most pet primates in the UK are kept in secret.

The young capuchin monkey that German authorities confiscated from Justin Bieber in 2013. Photograph: Christof Stache/AFP

The primate code is primarily to explain the welfare and management needs of the animals and a breach of its provisions is not actually an offence – though it could be used as evidence in court in animal welfare cases. The code, which applies to everything from gorillas to lemurs, is further weakened as it is subject to broad interpretation – specific groups are not covered in any real detail.

The keeping of some primate species, such as capuchins, is thankfully restricted under the Dangerous Wild Animals Act (1976), but many, including marmosets are not listed. A 2014 RSPCA report found that 81% of pet primates in the UK belonged to the marmoset group originally from South America.

Other primates, such as cotton-top tamarins, are critically endangered and should receive the highest level of legal protection from international trade.

With little awareness surrounding laws and a general lack of consequences for those failing to comply with regulations, many feel that the law should change and that a total ban on the keeping of pet primates in the UK should be introduced.

Rachel Hevesi, the director of Wild Futures, a primate sanctuary in Looe, Cornwall, knows all too well just how weak the current legislation is. “We’ve had over 150 primates come to us over the years and, without exception, every single one has had physical or psychological problems or, in many cases, both,” she says.

Hervesi wants to see a full ban on keeping primates as pets and sees success lying in a “positive list” style of legislation, where any specific primate species allowed to be kept as pets would be listed. With no species being proposed as being suitable, this blanket, prohibition-type law means that there would be little room for misinterpretation. Such legislation is already present in Belgium and several other European countries and has led to not only a reduction in the overall number of primates being kept as pets, but also to an increase in members of the public reporting illicit pet owners.

Primatologist and conservationist Jane Goodall. Photograph: Diana Sanchez/AFP

Hevesi is hopeful that the British government will bring a ban into force in the near future. When the primate code was introduced in 2010, it was agreed that the government would review its success after a five-year period. Defra failed to hold that review in 2015, but has since promised to reassess the legislation this year.

Key stakeholders including the Primate Society of Great Britain, the RSPCA, the British Veterinary Association, the British and Irish Association of Zoos and Aquariums (Biaza), Born Free and Four Paws all support a ban on pet primates and are gathering evidence and data for the government review.

Hevesi says: “The trade relies on the ignorance of the buyer and the greed of the breeders. We’ve never met a keeper who has deliberately set out to harm their primate pet; it’s a lack of awareness and skills.”

The image of primates as clever and interactive little human-like animals that can live alongside and play with us may seem appealing – and a recent batch of unthinking celebrities such as Justin Bieber, Beyoncé and the Kardashians posing with primates has only added to the problem – but without exception, every expert, academic, welfare officer and zoo keeper agrees that primates are wholly inappropriate as pets.

Whereas dogs and cats have been specially bred for generations as pets – to a point where we have selected specific behavioural and physical traits that make them perfect companions – most primates bred as pets are only the result of two or three generations in captivity and are, in most respects, still wild and untamed animals.

Renowned primatologist and conservationist Dr Jane Goodall has worked with wild and captive primates for decades and knows them better than anyone. “Every primate belongs in an environment that is as close to a wild setting as possible. They are beautiful and intelligent animals, but highly complex with very specific needs. They simply do not belong in our homes as pets.”

With such strong opposition to the UK primate pet trade, it is hoped that a ban can soon be drafted and introduced to protect the needs and welfare of these highly intelligent, though difficult to keep, wild animals.