The Children's Commissioner says 30,000 babies a year don't get the same support others do through the paid parental leave scheme and that should change.
The Government Administration Committee is considering a bill to lengthen the time parents are eligible for the scheme, from 14 to 26 weeks.
Commissioner Russell Wills' submission says that would be positive for families that are already eligible, but the criteria should be widened.
Currently a woman has to have worked for the same employer for at least 10 hours per week, for the six months just before the baby's birth.
Dr Wills said the scheme should include babies whose mothers might have worked for more than one employer, have done casual work, or have a strong history of employment.
Govt should fund extension - Plunket
Plunket says an extension of paid parental leave is something the Government should fund.
The Government Administration Select Committee is hearing submissions on a bill put forward by Labour MP Sue Moroney, to extend the scheme from 14 to 26 weeks.
Plunket senior policy advisor Clair Trainor said the extension would allow babies more time to form secure attachment to the family unit.
She said that would raise the health and wellbeing outcomes of more children.
Ms Trainor said extending the scheme is the socially responsible thing to do and it would outweigh the costs over the long term.