Already, four US companies are selling an assortment of the randy androids, aimed at both men and women, with names including Roxxxy Gold and Harry Harddrive. Prices range from just under £4,000 to £11,600 for the "Harmony" supermodel.

Unlike the mannequin-style sex dolls from which they evolved, the sexbots can adopt different positions, simulate sexual movement and even display orgasms.

They have silicon skins fitted with sensors that respond to touch, and some have pre-programmed emotions and personalities.

But the sexbots are not something to be sniggered at, according to artificial intelligence expert Professor Noel Sharkey.

He believes that, like internet pornography, they could have a major impact on society depending on their affordability and people's willingness to allow them into their lives.

A new report co-authored by the professor seeks to raise awareness of sex robots and issues grim warnings about the "dark side" of the rapidly advancing technology that could involve issues of rape and paedophilia.

Speaking in London, Prof Sharkey, from the University of Sheffield, said: "I can tell you that the sex robots are certainly coming. I can't think of any other way to say it.

"There are a bunch of companies making these (things) and beginning to ship orders in fact, and we thought policymakers and the public should really know what was going on."

In future, sex robots could be populating brothels, providing entertainment at stag nights and helping people live out guilt-free threesome fantasies, he said.

They could also offer therapeutic and helpful services to people with psychological problems or physical disabilities, and even pensioners with an unusual level of spring in their step.

At the same time, other aspects of the sex robot revolution could be extremely dangerous, said Prof Sharkey and colleagues from the Foundation for Responsible Robotics.

Compliant and uncomplaining robots could encourage objectification, abuse, rape and paedophilia.

Inanimate child sex dolls had already been manufactured and exported from Japan by a self-confessed paedophile, Prof Sharkey revealed.

They were not illegal in the US, but a consignment of the dolls had been seized in Canada, which has strict laws on representing children as sex objects.

One sex robot, Roxxxy Gold, made by the US company TrueCompanion, came with a choice of personalities including shy and reserved "Frigid Farrah" and adventurous "Wild Wendy".

A robot pre-programmed to resist sexual advances was effectively a rape victim, said Prof Sharkey.

"Some say it's better to rape a robot than a person, but others think it would encourage rape," he added.

It was impossible to predict how people might respond to sex robots, said the professor, but surveys had indicated a potential market out there.

In one poll conducted in the US last year, two-thirds of male and a third of female participants were in favour of using sex robots.

Another survey of 1,002 UK adults last year found that 17% of respondents would be prepared to go on a date with a robot. The proportion rose to 26% for a robot that looked exactly like a human.

Of 1,000 Americans questioned for a Huffington Post survey in 2013, 9% said they would have sex with robots if they were available.

While some of the sex robots, such as top-of-the-range Harmony, were extremely lifelike, this in itself presented a problem which could reduce their acceptance in society, said Prof Sharkey. He called it the "uncanny valley" effect.

"As a robot becomes more human-like, it gets creepier and creepier," the professor explained. "All these robots that are very human-like look like spooky psycho killers to me. You don't know if they're going to have sex with you or slit your throat."

At the other end of the scale from highly life-like robots were artificially intelligent sex toys, some of which were already available.

One new "AI dildo" could detect vagina muscle spasms and adjust itself to enhance an orgasm.

Other examples of "sex tech" included devices that allowed male and female users to stimulate each other wirelessly.

Last year, it was widely reported that a Swiss businessman planned to open London's first "fellatio cafe" staffed by robots who would be on hand to offer oral relief to male customers.

Prof Sharkey wanted to see the government take pre-emptive action to stop paedophile sex robots entering the UK.

"I would say there should be an import ban on those," he said.