A horrified mother went to the police after discovering the nanny she had hired for her daughters spent a fortnight showing them porn, teaching them about sex and making out with her boyfriend.

Helen Leah Ferriolo, 40, was supposed to be taking care of the two sisters aged eight and 10, along with their 10-year-old friend at the house in North Haven, Connecticut.

Instead they were locked in a closet and endured weeks of sexualized behavior, lewd comments and lessons in masturbation and oral sex, an affidavit claims.

Ferriolo repeatedly masturbated in front of the children and demanded that one girl sniff her fingers afterwards.

She also grabbed her breasts, asked her to ‘pose sexy’ in her bathing suit, and held her hands behind her back to make her watch a porn video.

The girls revealed their ordeal to their horrified families after Ferriolo was sacked for repeatedly not turning up to work.

The girls’ aunt recorded a call in which she confronted the nanny about her behavior and pretended she had a recording of her sexualized conversations.

Ferriolo claimed that the girls had initiated the talks before admitting she was sorry and ought to apologize to them.

‘I probably shouldn’t have said what I said,’ she reportedly confessed.

The nanny from Wallingford began working for the family on July 15 and would take the girls for days out at the beach in nearby East Haven.

‘You have big t**s, the boys are going to love you,’ she told one of the 10-year-olds as she changed.

On a second visit Ferriolo ‘began to touch and her rub (her) breasts’, before the girl pushed her away.

The nanny would also bring her boyfriend Tim McNulty to swim at the family’s pool without the parents’ knowledge.

‘Leah and Tim were on top of each other while in the water and were kissing,’ the affidavit records.

‘Leah took her bathing suit off. She did not see anything else when the bathing suit was taken off because she went inside.’

The elder sister was in her bathing suit at home when Ferriolo took out her phone and asked her to ‘pose sexy’, it is claimed.

The nanny then took a second photo after the girl turned round, but the girl waited until Ferriolo had left her phone unguarded before deleting the photos from it.

She allegedly told the girl’s friend to wear a ‘more revealing’ bathing suit, and showed the girls a video of her and her boyfriend in bed immediately after having sex.

The eight-year-old did not escape the nanny’s attention either and recalled her on the ‘couch rubbing her breasts and groin area under her clothing.

‘She advised (her) that she should try it, but she refused. (Ferriolo) also made lewd gestures in front of (the eight-year-old).

‘She described a particular incident where (Ferriolo) put her hands near her own mouth and moved them around in a circular motion.’

The little girl and her sister was repeatedly locked in a closet by their carer who banged on furniture to pretend there was an ‘intruder’ in the house.

Ferriolo was sacked on August 8 and the girls’ mother went to the police on August 20 after they began revealing what had happened.

The girls repeated the allegations in interviews with North Haven police and Connecticut Department of Children and Families.

The nanny was arrested on Friday and has been charged with four counts of risk of injury to a minor, three counts of second-degree unlawful restraint and a single count of fourth-degree sexual assault.

She has been freed on a $50,000 bond and is due to answer the charges at Superior Court in Meriden on October 3.