For mother-of-three Brooke Gibson, the cost of childcare is "unsustainable".

Before she met her current partner, the cost of childcare almost pushed her to the point where she decided it wasn't worth working, she said.

"When I was on my own I was paying over half my income in childcare costs and in the school holidays, when I had to pay for holiday programmes, it was even worse."

She now has a newborn, a four-year-old in daycare and a primary-school-aged child.

She worked part-time for an OPSM branch before her baby was born and earnt what she said was "not a bad hourly rate".  "However all I was doing was haemorrhaging money for childcare and I would've actually had more money in my pocket if I was on a benefit and would have more time with my kids."

Daycare cost $7 an hour and holiday programmes could run to many hundreds of dollars a week.

She is currently on maternity leave and unsure whether she will return to work.

Data from Stats NZ shows that 11 per cent of parents of children in formal childcare spend more than $200 a week.

Among those going to childcare centres, that increases to 16 per cent. Thirty per cent of parents of centre-attending kids spent $100 to $200 a week. 

Public kindergartens, kohanga reo centres, playcentres and organised home-based care were all cheaper. 

Before age three, subsidies are linked to income. If a two-child household earns more than $1800 a week, no subsidy is available until a child's third birthday. 

"The thresholds for childcare subsidies have not changed since 2010 although the rates have marginally. More and more families are having to work around their children earlier and pay for the expensive costs of childcare. If two children are under three then full-time childcare can cost around $500. If the household earns more than $1800 a week with two children then they don't get a subsidy - this is the equivalent of two full-time jobs at $22.50 per hour," Jeni Cartwright, communications adviser at the Child Poverty Action Group, said.

"If one parent earns $45 an hour for 40 hours a week they may be better off because the other parent may be able to work fewer hours and/or be at home with the children, thus saving them the childcare costs. The low-income two-earner family pays a disproportionate amount of their incomes on childcare,  and is therefore worse off. The model for childcare subsidies needs to change to support different household models of work, number of hours worked in the household for example as well as total income must be considered. Furthermore the threshold needs to be increased, so more families can get ahead through work."

New Zealand parents spend the second-highest proportion of average family income on childcare costs out of the countries in the OECD. United Kingdom topped the chart at 33.8 per cent, followed by New Zealand on 29 per cent and Ireland on 27.4 per cent.

The OECD's Society at a Glance report said it could have significant effects on families.

"Such high costs are a strong deterrent to employment. It may not be financially worthwhile for both partners to work." 

Full-time childcare only cost Swedish families 4.4 per cent of average income.

Jess Berentson-Shaw, of think tank The Workshop, said New Zealand needed free universal childcare if the country valued providing the best opportunities for all children and their parents.

"This is what a society that understands the foundations for wellbeing does. Where this is provided, in other countries, we see families able to take advantage of many opportunities for themselves and for their children.

"In Denmark policy-makers understand particularly that those parenting alone need additional support for childcare if children from all family types are to have good opportunities in life - we don't just privilege children living in specific family types. So there is additional support for children of those parenting alone.  We do need to be clear that good provisions or childcare can look like many different things- for example supporting those who look after their babies and children at home as well as those who use early childcare centres. Essentially policy-makers need to understand that raising children is never as straightforward as we think and policy to do it well needs to be flexible to the needs of different families and circumstances."