From next month, the service will be free only to high-needs patients.
ProCare chief executive Ron Hooton said the scheme was paid for from a fund that was specifically to improve access for high-needs patients through various programmes, with a top-up from the Auckland District Health Board, now ended, which had enabled the broader coverage.
He said that although the "Services to Improve Access" fund had received small increases during better economic times, no increase had been given for the coming financial year - and demand continued to grow.
Other health services in Auckland provide free sexual health services - such as Family Planning, the East Health clinics, both free for the young, and the four clinics run by the DHB which are free for people of any age.
However, ProCare-linked Botany GP Dr Marcus Hawkins, who is appalled by his group's restriction of its service, said the Family Planning clinic in his area did not provide a full range of services and was open only for half days.
"School students may have access to a school nurse but not to a doctor unless they are prepared to pay. Not all schools have nurses either."
He said those not eligible for free care might face fees of $30 if they were enrolled with a GP clinic, or $40-$50 as a casual patient.
Mr Hooton acknowledged that under ProCare's move "it is possible that teen pregnancy, abortion and STI rates could increase".
Youth health specialist Dr Simon Denny, of the University of Auckland, said, "We already have high rates of kids not going to see the doctor when they need to, especially young people who are sexually active. This is just going to make further barriers for them."