A nanny charged with sexual assault is accused of engaging in “lewd activity,” cops said.

Helen Leah Ferriolo, 40, of Wallingford, Connecticut, had been working for a family in North Haven for about two weeks before she was fired for repeatedly not showing up to work, according to the arrest warrant affidavit obtained by the Daily Mail.

The document detailed that Ferriolo had been babysitting the family’s two children, ages 10 and 8, and another 10-year-old girl.

Less than two weeks after Ferriolo was let go, the sisters told their parents about the ex-babysitter’s alleged behaviour.

The family went to police to report Ferriolo, who they accused of having inappropriate conversations with the three children, making lewd gestures, making out with her boyfriend and masturbating in front of them, the affidavit states.

Ferriolo also changed in front of them, watched as the girls changed, and let her boyfriend watch, the children alleged.

The woman allegedly grabbed one of the girl’s breasts, asked her to “pose sexy” in her bathing suit, while telling the girl’s friend to wear a “more revealing” swimsuit.

She also allegedly held one of the girls’ hands behind her back to make her watch a porn video, according to the affidavit.

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In another bizarre instance, the sisters claim Ferriolo locked them in a closet as the woman banged on furniture to pretend there was an intruder in the home.

Several members of the family called the accused to confront her of the allegations, the affidavit read, but she denied the allegations.

Ferriolo claimed it was the children who initiated the talks before allegedly admitting she was sorry and that she ought to apologize to them.

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

The affidavit said investigators interviewed the three children, who all provided similar accounts of their interactions with the nanny.

Ferriolo is charged with fourth-degree sexual assault, four counts of risk of injury to a child, and three counts of second-degree unlawful restraint.

She was released from jail on $50,000 bond and is set to appear in court on Oct. 3.