An 11-year-old boy has become a father in New Zealand after conceiving a child with the 36-year-old mother of his school friend.

The woman, who cannot be identified for legal reasons, allegedly coerced the primary school pupil into repeated sexual encounters over a period of time before becoming pregnant.

Police were alerted by the child's principal after the boy approached him toward the end of the 2012 school year to confess his problem.

He said that student, who is now 12, told him, "You won't be very happy with me" before admitting he was having sex with his friend's mother and wished to put a stop to the liaison.

Child Youth and Family took custody of their baby two months ago.

A Child, Youth and Family Services spokesperson confirmed CYFS was involved with the unique case and the woman was facing criminal charges. However, the woman denied there was sexual contact between them.

"This case raises an important point. I will seek advice from officials on whether or not a law change is required," Justice Minister Judith Collins said in a statement.

Under New Zealand law rape is only applicable when males forces sex, which carries a maximum sentence of 20 years. Females who force their unwilling partners to have sex are charged only with sexual violation.

Ken Clearwater, the manager of Male Survivors of Sexual Abuse, commenting on the case, said, "As a male you're supposed to enjoy it but we don't say that about young girls. Males are not seen as victims. The psychological damage is huge - and they carry extra shale because it's a woman and you're supposed to enjoy it."