Less than half of all new parents have applied for paid parental leave from the government.
Figures released by Inland Revenue today show the number of people who received at least one payment of paid parental leave in the year to March the 31st was 25,599, while there were about 58,515 births registered during that period.
The trend has been consistent over the past 10 years, with an average of 42 percent of new parents benefiting from the scheme.
Spokesperson for parenting lobby group 26-for-Babies Rebecca Matthews said the casualisation of work may be stopping people from accessing payments.
"Many people have not been eligible, so any review of eligibility, which is currently underway, should be as broad as possible," she said.
"We want this worked out so that everyone who is in work when they have a baby can take parental leave - it's a work right."
Currently, parents are eligible for 14 weeks parental leave if they have worked for the same employer, or have been self-employed, for an average of at least 10 hours a week in the six months immediately before their baby's expected due date.
But the National-led government announced in May it would extend the paid parental leave to 18 weeks over two years and would carry out a review on proposals to broaden eligibility.
The consultation process closed last month, and the Ministry of Business, Innovation and Employment is reviewing submissions before reporting back to the government.
Inland Revenue figures also reveal the number of parents receiving payments flatlined since 2007, despite about 138,200 more people, including about 70,000 women, joining the workforce during that period.
