Border force officials have seized 18 consignments of child sex dolls sent from overseas since 2013.

The life-size dolls, which resemble children as young as five and are sold wearing lingerie, have movable joints and come with heating instructions.

A child sex doll manufacturer claims they can be used to help paedophiles control their urges.

But experts have said there is no evidence to support claims that using dolls prevents child abuse and warn that products normalising children in sexualised ways could reinforce paedophilic behaviour.

More than 60,000 people signed a petition this year to ban the "sickening aids for paedophiles" being sold in Australia.

A Department of Immigration and Border Protection spokeswoman said the possession of "anatomically correct child dolls" was already an offence because they were considered child exploitation material.

"The Australian Border Force works closely with the Australian Federal Police and state police agencies to target and seize this objectionable material at the border, and bring before the courts those that seek to possess or are in possession of a child sex doll," she said.

Trottla, a Japanese business widely reported to sell the dolls online, promotes more than 100 dolls on its website and says it supplies clients around the world.

According to the Trottla website the prepubescent-looking dolls are not for sex, but they are featured in its online galleries in various stages of undress and in sexual positions.

Trottla founder Shin Takagi has described himself and most of his male clients as paedophiles, although he said he has never acted on these impulses. He said the dolls can "substitute a human girl".

In an interview with The Atlantic earlier this year, Mr Takagi said he was "helping people express their desires, legally and ethically".

"We should accept that there is no way to change someone's fetishes," he said. "It's not worth living if you have to live with repressed desire."

In an email Mr Takagi declined an interview with Fairfax Media. He said he would not comment while the petition to ban the sale of child sex dolls continued to use an image from his website without permission.

"I am an artist," Mr Takagi said last week. "Both the doll and a photograph are my works entirely, and I own the copyright."

Child-like sex dolls are considered objectionable goods that are likely to cause offence and are therefore prohibited from being imported into Australia.

Penalties for importing the dolls carry heavy fines of up to $450,000 and 10 years' imprisonment.

A 44-year-old man jailed earlier this year for possessing and disseminating child abuse material is understood to have owned a child sex doll.

In 2014, a 32-year-old Sydney man was charged with owning child abuse material after federal police raided his home and found a life-like child doll with a removable silicon genital insert in his bed. That matter is still before the courts.

An Australian Federal Police spokeswoman condemned all forms of child exploitation, including sexual gratification activities using items depicting children.

"The AFP continues to work closely with the Australian Border Force and state police agencies to bring before the courts those that seek to possess or are in possession of a child sex doll," she said.

The child sex dolls seized by border force officials have been destroyed or are pending further investigation, a government spokeswoman said.