A surge in seizures of child-like sex dolls by border officers has led investigators to identify dozens of previously unknown suspected paedophiles.
The lifelike silicone sex aids, which weigh around 55lb (25kg) and can cost thousands of pounds, are being imported into the UK after being sold by traders on sites including Amazon and eBay, the National Crime Agency (NCA) said.
The dolls, often manufactured in China and Hong Kong, are a "relatively new phenomenon" in the UK and should be criminalised, the operations manager at the NCA's Child Exploitation and Online Protection Command (CEOP), Hazel Stewart, said.
Border Force officers have seized 123 dolls in little more than a year since March 2016 and so far seven people have been charged with importing them, including one man who was jailed last month.
The figures were revealed as a judge at Canterbury Crown Court dismissed an attempt by ex-primary school governor David Turner's barrister to argue that a doll he imported was not obscene.
Former churchwarden Turner, 72, pleaded guilty on Monday to importing the child sex doll after the application to dismiss the charge was turned down.
Of the seven men charged with importing the dolls so far, six also faced child porn allegations.
Dan Scully, deputy director for intelligence operations at the Border Force, said this showed those who ordered the models often strayed into sex crimes.
"Border Force intelligence and detection officers started to notice an increase in prevalence of seizing these child-like dolls.
"What's critical, I think, for this investigation, these items were going to individuals, in many cases, who were committing other offences in relation to harm of children," he said.
"They were also, critically, people who were otherwise unknown to UK law enforcement in having an interest in sexual activity with children.
"By identifying these importations, working with partners, what we've identified is a whole set of people with interests in sexual activity with children who were completely unknown."
The NCA, CEOP and Border Force launched a joint investigation in March last year and asked a paediatrician to examine some of the models seized to confirm their belief that the dolls were child-like in appearance and anatomy.
Border Force officers have powers to seize items they believe are indecent or obscene under customs legislation, with those who ordered them prosecuted under a specific charge of importing an indecent or obscene article.
While NCA agents do not believe any similar models are being manufactured in the UK, Ms Stewart said there were concerns over a gap in legislation because it is not illegal to own a child sex doll.
Ms Stewart said finding which legislation to prosecute offenders under was a "head-scratcher" at first.
"Certainly the work our colleagues at the Border Force brought to us was new," she said.
"Their usual seizures don't include this type of article, it's more the traditional criminality of guns and drugs."
Mr Scully admitted it was not always possible to search every box going through customs and rely on officers to spot the hallmarks of a child sex doll delivery, which are often labelled as something else.
Ms Stewart admitted investigators were "playing catch-up" and many of the investigations into the seizures, which were mostly of a single doll bought by one individual, were at a very early stage.
Some cases which were marked "no further action" at the start of the investigation will also be reviewed and further prosecutions expected.
Asked if there should be new laws to combat the rise in child sex dolls, Ms Stewart said: "I think it's got to be through the full range of this criminality, from manufacturer to sale, to import, to possess - the full range.
"And we need to make sure it's future-proofed in case there is the introduction of the sexbots, the sex robots."
Ms Stewart said the dolls were unlike those people might associate with stag dos and were the precursor to more sophisticated child sex robots, which she warned were "just around the corner".
"They are the weight of a seven-year-old child, they are not something that is the traditional blow-up doll," she said.
"(They are) very, very different - very, very more accurate anatomically."
The dolls, with their unnerving glass-eye stare, false eyelashes and crooked fingers and toes, often come packaged with accessories including a choice of wigs, a USB device to warm the spongy silicone skin, and a cleaning device.
The men who import them often buy clothes to dress them up in, with examples including a lacy thong, negligee and pink lacy crotchless body stocking, Ms Stewart said.
Andrew Dobson, 49, of Merrivale Road, Wistaston in Crewe, was jailed at Chester Crown Court in June for two years and eight months in what is thought to be one of the first prosecutions for importing a child sex doll in the UK.
And the trial of issue at Canterbury Crown Court in the case of Turner, of Hollicondane Road, Ramsgate, was described as setting an "important" precedent in how suspects can be prosecuted.
Turner was unable to be sentenced on Monday because a pre-sentence report had not been prepared. Judge Simon James said the importation of a child sex doll was an "unusual offence" and that it "adds a degree of complexity".
He was freed on bail to be sentenced on September 8 for the importation charge and for pleading guilty at an earlier hearing to possessing or making more than 34,000 indecent images of children aged around three to 16.
Jon Brown, head of development at the NSPCC, said: "There is no evidence to support the idea that the use of so-called child sex dolls helps stop potential abusers from committing contact offences against real children."
The charity also called on the Government to criminalise the manufacture, distribution and possession of the "grotesque" dolls.