Families face paying more than $40 for a child aged 10 to see a doctor in many areas - even after taxpayer subsidies are taken into account.
In Auckland, around 40 general practices charge "co-payments" of $40 or more for children aged 6 to 17. Three charge $50 or more, which puts them among a handful of clinics nationally with top-end prices, even for office-hours fees.
The average fee for a medical visit in Auckland and nationally is around $22 for 6 to 17-year-olds. The higher-charging clinics tend to be in rich areas, such as the Parnell Medical Centre ($50), and the cheaper clinics mostly in middle- or lower-income suburbs, such the Kingsland Family Health Centre ($27) or the Otara Union Health Service (free).
But the Government says more than a third of enrolled children aged 6 or older are patients of the "very-low-cost access" clinics which get higher subsidies in return for limiting their fees; in the 6-17 age group the cap is $11.50.
No fees are charged for children of these ages at 93 clinics in the country, which helps to lower this age group's average fee to $7.64.
For children under 6 - the most vulnerable to ill-health - the national average fee is 69c and 95 per cent of these youngsters now get free visits to the doctor, day or night. Some clinics still impose substantial fees after-hours for infants, including $25 for a medical consultation at Ascot White Cross in Greenlane, the closest clinic for low-income Glen Innes.
Auckland's highest advertised fee for 6- to 17-year-olds is $60, according to the Auckland District Health Board website. It is at Family Doctors at Smales, in wealthy Takapuna, for children who are signed up through the clinic with primary health organisation ProCare.
But practice manager Jo Bennett said it charged $40 for enrolled children aged 6 to 17, which hadn't changed since the clinic was set up in 2011. The higher price is listed with the DHB because of funding rules.
The Green Party is concerned by the sudden rise in fees for many children once they turn 6 and wants more money injected into primary care so the patient's part of the fees can be reduced.
Greens health spokesman Kevin Hague pointed to the ministry's latest national Health Survey, which found that cost had prevented around 7 per cent of children aged 6 to 14 from seeing a GP for a medical problem in the preceding months.
A study of people aged 15 to 24, published in 2009, found a much higher rate of deferral of doctor's visits, at just over 20 per cent.
Rates of hospital admissions for some leading conditions that could have been treated in primary care if caught early enough, notably serious skin infections, increased for people aged under 25 in the decade to 2010.
These studies suggest the issue identified by Mr Hague predates the current National Government and existed under Labour, even though it greatly expanded primary care subsidies and reduced patient fees.
"Primary care saves you money in secondary care," he said. "For a government trying to maximise the health of its population, which is what we would be trying to do, if you can deal with problems by preventing them through public health or dealing with them in primary care, you minimise time away from study that a person has and you minimise the impact of illness on welfare, growing and learning."
In government, the Greens would push for more money to go into primary care subsidies, in return for an "across the board" cap of $11.50 on fees for the 6 to 17s, and if possible reducing that further, Mr Hague said. He didn't know how much that would cost but said Health Minister Tony Ryall had changed the health funding balance to favour elective surgery and specialist services at the expense of preventive and primary care.
Child Poverty Action Group member Dr Nikki Turner said its priority was universally free, 24/7 access for under-6s because of that age group's high burden of disease, but it also advocated moving towards free access for all children.
She said the prescription fee of $5 for each medicine for people aged 6 or older was an extra barrier.
"Loads of our infectious diseases have this poverty-related gradient. Poor kids get sick more often and have trouble accessing primary healthcare services."
Government funding for primary health care has increased from $620.7 million in 2007/8 under Labour, to $758.6 million in 2011/12 under National.
Mr Ryall said this included an increase of one third in funding for the very-low-cost access practices.
He also highlighted improvements in primary care, such as the increased access to diagnostic tests and minor surgery and the greater use of nurses, for instance in treating serious skin infections in the community with intravenous antibiotics, traditionally often a hospital procedure.
General Practice NZ medical director Dr Bev O'Keefe also drew attention to such advances, but said she and colleagues "vigorously resisted" the very-low-cost access scheme because state-capped fees never kept up with costs, leaving practices financially unsustainable.
The scheme under Labour was open to any practice that agreed to the fees caps, although National restricted entry to those with at least 50 per cent high-needs population, defined as Maori, Pacific or low income.
Dr O'Keefe said more targeting was needed, such as removing children's subsidies for high-income families.
GPs fees for Northland, Rotorua, Waikato and Bay of Plenty