A young woman was refused the birth control pill because she had not yet done her "reproductive job".
Melissa Pont, 23, said her family practitioner, Dr Joseph Lee, would not renew her pill prescription, instead lecturing her on a baby's right to live and on using the rhythm method, an unreliable family planning technique that involves having sex only at certain times of the month.
The Women's Health Action Trust said it has a "simmering issue" with GPs who will not prescribe contraceptives.
"Contraception is a basic health right for women," said senior policy analyst George Parker. "That should take precedence over a doctor's personal beliefs."
The NZ Medical Association said doctors can refuse treatment in non-emergency situations if their beliefs prohibit it - but they are required to refer the patient to another doctor.
Lee was initially reluctant to do that, Pont said, and she was concerned other women in her situation might not have had the confidence to argue back.
"I felt like my decision to not have children yet was being judged. That's a decision me and my fiance made," she said.
"We're young and we just bought a house and who is he to say whether we should have children or not?"
Lee, a doctor at Wairau Community Clinic in Blenheim, stood by his views and actions. "I don't want to interfere with the process of producing life," the Catholic father-of-two told the Herald on Sunday.
Lee also does not prescribe condoms, and encourages patients as young as 16 to use the rhythm method.
Teen pregnancy might be a girl's "destiny", he said, and it was certainly not as bad as same- sex marriage.
The only circumstances in which he would prescribe the contraceptive pill would be if a woman wanted space between pregnancies, or had at least four children.
"I think they've already done their reproductive job".
He acknowledged natural birth control was "not very reliable".
"That's the best thing about it. You can't choose it, you just have to be committed to it."
Family Planning national nursing adviser Rose Stewart said doctors should remember they were gatekeepers for a service, she said, and a woman's conscience was as important as theirs.
Medical Council guidelines say personal beliefs should not affect the advice or treatment offered, and should not be expressed in a way that exploits a patient's vulnerability or is likely to cause them distress.
Wairau Community Clinic lead GP Scott Cameron said a pamphlet at reception warned that some doctors did not prescribe birth control, and staff tried to screen patients. He would consider installing a sign.
The clinic is run by the Marlborough Public Health Organisation. Chief executive Beth Pester said Lee's choice not to prescribe was "his ethical choice", but she was concerned he discussed natural birth control with patients as young as 16, and would talk to him about that.
- Additional reporting John Weekes