"Well, teenagers do get sick. In fact, they have complicated needs, like mental illness, and sexual health issues, which can damage them forever if left untreated."
The policy was designed to reduce hospital admissions, prevent unwanted pregnancies, detect and treat mental illness, and take the pressure off parents at a stressful time in a child's life.
"It's bloody hard being a teenager, no matter where you live or who your parents are. And it's bloody hard for their parents too," Mrs Turei said.
A policy paper noted that consultation fees could be up to $56 for teenagers.
The Healthy Teens, Healthy Futures scheme would allocate $21 million a year to extend free GP visits to 290,000 teenagers and abolish prescription charges.
A further $8 million would go towards helping GPs manage the extra workload.
GPs could opt out of the scheme if they did not think the subsidies would cover their costs.
The policy also included a commitment to negotiating with district health boards and private clinics to ensure after-hours visits were free for all children under 18.
Government questioned how the new policy would be funded, and whether it would require cuts in other areas or tax increases.
Health Minister Tony Ryall said left-wing parties were now "in a desperate bidding war promising free everything to everyone".
In a speech that was mostly focused on children, Mrs Turei also took a shot at the National Government's environmental credentials, saying they were trashing the Resource Management Act and poisoning New Zealand's rivers.
The Child Poverty Action Group (CPAG) said the policy would make a real difference to teenagers' health.
"CPAG has advocated for free healthcare for under-18s for many years," CPAG spokeswoman associate professor Nikki Turner said.
"Access to good health care in the teenage years is just as important as it is for younger children. These years are crucial to people's long term health and investing more in teenagers' health and well-being has major benefits for society.
"The teenage years can be very challenging and it would make a significant difference to remove the cost barriers that currently stop many teenagers getting the primary health care they need."
Mrs Turei said New Zealanders faced a stark choice at the September election.
"Voters can choose National and its Cabinet Clubs, Charter Schools and crazy hangers on, and we will all watch while a tiny few get rich as a result.
"Or we can have a truly progressive government committed to giving everyone a fair go."
Co-leader Russel Norman will speak tomorrow, when he is expected to launch the party's climate change policy.
