A legal loophole allows paedophiles to legally download grooming manuals from the 'dark web', the Sunday Independent has confirmed.
The 'instruction manuals' provide graphic information on how to 'safely' groom children for sex.
While it is an offence to possess indecent images of children, the law does not specifically cover the possession of written material that gives advice on how to identify and groom victims.
The Department of Justice has confirmed there are no immediate plans to crack down on predators downloading the illicit material from so-called 'dark net' sites.
The dark web is a hidden area of the internet beyond the reach of Google, where users can operate anonymously.
The sites are virtually untraceable global networks, which in some cases are almost impossible to police.
Security sources say its use as an international market place for firearms, drugs and indecent images of children is continuing to rise.
In 2014, the department said it planned to review legislation to examine whether to close the loophole.
However, it has now confirmed no action has been taken to clamp down on an area of growing concern for child protection services.
In a statement, the department stressed that the Criminal Law (Sexual Offences) Act contains a number of new offences to fight the exploitation of children.
These include inciting or causing a child to become involved in prostitution, or the production of child pornography.
Maeve Lewis, chief executive of One in Four, said it was "appalling" that abusers could download the material without fear of prosecution.
She warned that sex offenders generally continued to abuse until they were caught.
The organisation provides support for adults sexually abused in childhood, and operates a sex offender intervention programme.
"The fact it's not illegal is unthinkable.
"Last year, we worked with 46 sex offenders as part of the programme. Almost a third were aged 18 to 25.
"The vast majority began their offending at a very young age, downloading images of child sexual abuse.
"The internet is hugely problematic. Through smart phones and other devices, children now have access to completely inappropriate material. And most parents don't have a clue what their kids are looking at.
"It's a great worry for fathers, mothers and educators that children may become sexualised by these images, and actually go on to become sex offenders."
One in Four's annual report reveals 40pc of its 800-plus clients last year were male.
Ms Lewis says this challenges the idea that boys are less likely to be sexually abused.
Almost half (46pc) of those counselled said they were abused in their own families - with strangers accused in one-fifth (19pc) of cases.
Catholic Church figures, friends and neighbours were each said to be responsible for one-tenth of abuse, while 9pc were abused by more than one person.
One in Four said that its clients had a "very good experience" with gardai, but described the criminal court proceedings as "demeaning, humiliating, and re-traumatising".
Meanwhile, experts point out the internet comprises three different layers: the surface web, the deep web, and the dark web.
The top surface layer is the part most users access by using search engines such as Google.
The deep web contains pages that search engines cannot access, and that remain hidden without the use of a relevant password, such as company intranets accessible only to employees, or online banking apps.
Beyond the deep web lies the dark web - a secret section of the online world that is accessible only by using software - which allows users to remain untraceable.
The dark web is essentially an online black market, a place where those involved can trade in illegal items, and purchase illicit materials, using digital currencies such as Bitcoin.