After the presentation, Business NZ employment relations manager, Paul Mackay, told reporters the additional proposed leave allowance may cost more for employers as parents would lose their sharp edge in their workplace.
Mrs Austin - herself a former employer - said she agreed with the claims.
"There's a heap of costs involved.
"When a person goes off on maternity leave, they're guaranteeing their job for when they come back.
"But who's going to take it over while they're away - they've got to retrain people," she said.
Employment law specialist Blair Scotland, of Chen Palmer Law Firm, said extending the period was unlikely to make any difference to people who already discriminated against women because of leave allowances. "Regardless of what you do, there will potentially be a very small percentage of employers out there who will do that."
Mr Scotland said it was unclear how additional training costs could be associated with longer leave allowances.
"Parents, men, women can take up to that 52 weeks [unpaid parental leave] anyway.
"It's difficult to see where that additional cost comes from," he said.
Ms Moroney said the Business NZ submission was outdated and unfairly singled out women. "It is out of step with what I understand modern-day employer attitudes are towards women and I cannot explain, for the life of me, why an organisation like Business NZ would come to select committee with this type of written submission."