A teenage boy who had sex with his 32-year-old neighbour claims he was taken advantage of and robbed of his childhood - and his mother is calling for tougher penalties for female sex offenders.

Cecelia Rona Hale, 32, is due to be sentenced this month after admitting two charges of sexual conduct with a young person under 16 years and one charge of supplying cannabis to a person under 18.

The South Auckland boy, who was 13 when he started a sexual relationship with Hale, is alleged to have fathered a child with her. The child is in the care of Child Youth and Family.

The boy's mother, who cannot be identified to protect her son, said there is a double standard when it comes to punishing male and female child abusers.

A woman cannot be charged with rape because of the way it is defined under New Zealand law.

"If a woman does the same crime as a man, they should do the same time. They want to have equal rights and all that, but when it comes down to the crunch, it doesn't work like that," she said.

She added that Hale had ruined her son's life and he will never be a normal teenager. "I am angry and hurt. That's my son, that's my boy.

"She took his childhood away.

"You know, a mother is there for nurturing a child, not to rape a child. She's got three kids of her own, how would she feel if I'd done that to her kid?"

The mother said Hale, who nicknamed herself "Gurl", befriended the family after they moved next door in May 2012. "We thought she was a pretty cool cat, she went out of her way and came over here to introduce herself and made us feel comfortable," she said.

The boy said he started a sexual relationship with Hale against his will two months after he turned 13. He was best friends with the Hale's son and would often go next door to play Xbox and "talk like bros do".

During the school holidays in July 2012, Hale invited the boy to stay overnight after hearing his mother's boyfriend was visiting.

She then gave the boy alcohol and asked him if he wanted to sleep with her - he says he said no and tried to leave.

"I didn't want to . . . but these things just happen," the teen said.

The pair had sex several times and he later learned Hale was pregnant.

"I was pretty shocked . . . I had butterflies straight away," he said.

In September 2012, the boy confessed the pair had been in a sexual relationship, and his mother went to the police.

The mother, who has three other children, said the offending had a negative impact on her entire family because her son's behaviour has become "ugly" and he is "out of control".

Since the offending came to light, the teen has been to two different schools and she has tried to homeschool him, but he refuses to learn because he "feels older" and "more worldly" than kids his own age.

"[Hale is] a nasty, evil woman. I hate her for what she's done to my son. He was a decent boy, I could control him, I can't control him now," the mother said.

After the offending, Child Youth and Family tried to take the boy out of his mother's care.

"He doesn't need to be uplifted. He needs help," his mother said.

And while the family awaits the results of DNA tests to confirm the baby's paternity, the mother wants to look after the baby.

"The baby is his. He looks identical to [my son]. We've got two more weeks to go until the DNA test results come back."

She added that they had been able to see pictures of the baby only on Facebook.

Anyone found guilty of sexual connection with a child under 16 faces a maximum of 10 years in prison. The maximum penalty for rape is 20 years' jail.