Thousands of women appear to be using the internet to share sexual fantasies of abuse involving children.

An investigation by The Independent on Sunday found a series of websites that depict female-perpetrated child abuse as "natural, educational and enjoyable" for children.

Users log into online forums to meet other "like-minded" web users and to share personal childhood experiences about sexual acts with adults that they say include mothers, teachers and babysitters. User profiles on one website monitored by the IoS claimed to be those of teachers, doctors and retired grandmothers with an interest in "young girls" and "lesbian incest".

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The postings on such sites – assuming they are not posted by men – run counter to the widely held belief that female abusers are either anomalies or feel forced into such depravity by abusive men. Many of the users appear to have easy access to children and describe deriving sexual gratification from sharing their fantasises.

The discovery comes just days before three women are due to be sentenced for a range of sexual offences involving children.

Vanessa George, a nursery school teacher and mother of two, and Angela Allen, a single mother, were part of an online paedophile ring uncovered last summer after police were alerted to sadistic photos they were emailing to each other and a male paedophile, Colin Blanchard. The three met on Facebook and only ever communicated by email or text.

Carol Clarke, 46, will also be sentenced this week in Grimsby after she admitted following boys and girls and abusing them in public toilets.

Dr Anne Carpenter, a clinical and forensic psychologist in Glasgow, said: "The internet is presenting clinicians with completely new dilemmas and new questions. We don't know if interaction on these websites translates into offences, but while many may be able to stop at the fantasy level, we cannot ignore these sites and assume people won't act on these fantasies. They may be fewer in number, but women are as accountable for their actions as men. Being a victim of abuse doesn't mean a woman can't be dangerous."

The IoS findings are supported by research carried out in a study in Ireland, which found that women were using such websites to justify their feelings as "natural". Many of the women used the forums, chatrooms and "frequently asked questions" to share tips on how not to get caught – for example, by exploiting situations such as bath time or breastfeeding.

They share many of the same beliefs as men who abuse children: that having sex with a child is educational and children are sexual beings.

An excerpt from one website reads: "If you are a female child lover we want you to know there is nothing wrong with you. The biggest problem is the teachers, therapists, cops, clerics and parents who force their stale morality on the young people in their custody. For children, experiencing sexual pleasure is not damaging at all, they enjoy it ... just like we do." A discussion forum on another website details myriad claims of abuse. "Julie", 32, wrote: "My first real kiss was from my mom, I was about 6/7, she had been on her own a long time I guess ... it was a bit scary, but she was so loving and I just loved the way she held me ..."

While the majority of the 1,200 registered users on the website do not reveal details about themselves, 25 say they live in the UK. Although no abusive images were posted, much of the text is too disturbing to print.

Very little is understood about whether use of these websites encourages actual abuse. The Metropolitan Police's paedophile unit, which targets the activities of paedophiles online, has told the IoS that it is unaware of any female-specific websites. None of the 115 people arrested by Europol for alleged child sex offences last Thursday – after a two-year operation – were women. Last week we passed details of our research to the police.

Dr Sharon Lambert, a forensic psychologist who carried out in Ireland some of the few studies in the world on this subject, said: "It is only in the past decade that we have started to understand how males engage with and are affected by online paedophilic material. Now is the time to lift the taboo surrounding female offenders and to engage in some research that attempts to understand these emerging trends. Deviant female sexuality is under-researched and requires attention."

Susannah Faithfull (no connection to the Faithfull Foundation) survived years of sexual and physical abuse perpetrated by her mother. Her therapy service, Aurora, has received a 25 per cent jump in calls from survivors of female abuse since news of Vanessa George's crimes.