By Mark Kinver
Science and environment reporter, BBC News
Joey, a rescued capuchin, was kept in a "wardrobe-sized cage" for nine years
A loophole in animal welfare laws that allows primates to be kept as household pets should be closed, an MP has urged.
Mark Pritchard, Conservative MP for The Wrekin, said the animals, such as small monkeys, were often housed in cramped cages, causing unacceptable suffering.
The RSPCA supported the call for a ban, adding that an estimated 3,000 primates were being kept as pets in the UK.
Mr Pritchard is calling on ministers to outlaw the breeding, sale or keeping of primates for the domestic pet market.
The Shropshire MP said he would use his Ten Minute Rule Bill, which he will present in the Commons on Tuesday afternoon, to highlight why the practice of keeping the animals had no place in modern society.
"Are we a modern country or are we a country stuck in Victorian times that likes to keep primates in confined spaces in order to entertain us," he told BBC News.
As well as welfare concerns, Mr Pritchard added that his proposals would also raise awareness of how the market for exotic pets could undermine global conservation efforts.
"Britain needs to lead the world on this issue and set a global standard in order that other countries follow and ban keeping primates as pets.
"The demand for so-called exotic pets is growing and the problem is getting worse rather than diminishing; and in my view there is a clear correlation between the scarcity of some of these species and the pet trade.
"Unless the government takes action to stop primates being kept as pets in the UK, their rhetoric on protecting forests and ecological habitats rings very hollow indeed."
Recently, the IUCN - also known as the the World Conservation Union - published its latest global assessment on the state of the world's primate species.
The Red List found that 48% faced extinction; a situation described as depressing by some conservationists.
"We certainly support Mark Pritchard's aims," said Rachel Hevesi of the Monkey Sanctuary Trust.
"We would like to see an end to the primate pet trade because it only causes suffering and, in the bigger picture, only damages the conservation of primates.
Although the vast majority of primates for sale in the UK - primarily small monkeys like marmosets, tamarins and capuchins - were bred in captivity, Ms Hevesi said the animals' exact trade routes were unknown.
"We know that there is a lot of legal and illegal trade coming out the native range countries into Europe," she told BBC News.
"By the time that the monkeys arrive in this country, the monkeys are claimed to have been captive bred.
An X-ray of Joey revealed signs of bone disease and deformities
"Therefore it is virtually impossible to know what direct and indirect links there are back to the native range countries.
"As long as there is a legal trade, it will feed an illegal one too."
One of the recent arrivals at the trust's sanctuary in Cornwall was a capuchin named Joey, who had been kept in a wardrobe-sized cage for nine years.
A vet's report said an X-ray revealed that the monkey showed "extensive boney deformation and generalised poor bone density" as a result of being kept in cramped conditions and not getting enough sunlight.
It added: "New World primates, such as the capuchin monkey, are particularly susceptible (to bone disease), due to their specific requirements for vitamin D3."
Joey is believed to have been a wild animal, taken from a forest in Suriname, South America.
Although keeping many small monkey species, such as tamarins or squirrel monkeys, as a pet do not require licences, capuchins are covered by the Dangerous Wild Animals Act.
This legislation requires the animals to be licensed and to be examined by a vet once a year.
Yet an investigation should that Joey's owner's initial 12-month licence was never renewed.
Ros Clubb, scientific officer for the RSPCA's wildlife department, said a ban on keeping primates as household pets was something the society had been calling for over a number of years.
"The general public should not be able to keep them because the primates have such specialist needs that they cannot be met in a household environment," she told BBC News.
Rescued primates often show signs of physical or psychological damage
"They don't get the stimulation they need, they don't have the room they need. Often, diet is a problem as well.
"They are also not exposed to the level of sunlight they need and they often develop all sorts of psychological and behavioural problems because of the way they are being looked after.
"At present, there is virtually no restriction for keeping primates as pets."
Dr Clubb added that it was an issue that the government was looking to address.
Concerns about keeping primates as pets were raised during the formation of the Animal Welfare Act 2006, and the government established a working group to devise a code of conduct.
The government had indicated that it was preparing to reconvene the working group, of which the RSPCA is a member, in the coming months.
Dr Clubb said that the society had a very clear position: "What we have been calling for is for this restriction to be part of the legislation.
"That would mean that there would be a restriction on who would be able to keep primates in the first place.
She added owners should be limited to organisations or individuals who were part of a registered conservation programme or housed rescued animals.
The likelihood of Mr Pritchard's Bill making it to the statute books is remote, but he said that his goal was to get the issue back on the political agenda.
"It is putting down a marker that the government needs to take up the cause for itself. This Bill has cross-party support, including one of the most respected animal welfare supporting Members of Parliament, Elliot Morley.
"This is not a partisan matter, it is a matter about what does it say about our country."