"Anyone and everyone is welcome! We actively encourage anyone who ISN'T a BFing mother to attend!" she wrote on Facebook.
"This is merely a show of people who are demanding that the legal rights of a breastfeeding mother is recognised and acknowledged. We will be using this opportunity to further highlight the need for education to support breastfeeding mothers," the event notice claims.
A Kmart spokesperson told the Herald the company is upset over the incident.
"We were concerned to learn of our customer's experience and have asked her to contact us directly. Kmart has an equal opportunity policy in place which clearly states that the business will not tolerate unlawful discrimination or harassment on the basis of pregnancy, potential pregnancy or breastfeeding and the features associated with these attributes.
"Kmart sincerely apologises for this situation."
The popular family shop sells a range of breastfeeding and baby equipment.
While the Australian Breastfeeding Association said a mother's right to breastfeed in public places is protected by law throughout the country, in New Zealand, according to the Human Rights Commission, there is no specific law that deals with the right to breastfeed.
However, legal protection is available in situations where disadvantageous treatment can be proven or direct or indirect sex discrimination occurs.
- Additional reporting, NZ Herald