"If this behaviour is continuing, we recommend you take immediate action to address our concerns and seek legal advice about complying with the Fair Trading Act."
The Commerce Commission began investigating complaints from consumers in April 2016 who had sought remedies for faulty Apple products.
It also investigated information on Apple's website, sales and refund terms and conditions for online Apple Store purchases, and documents provided with replacement products.
Commissioner Anna Rawlings said Apple had told some customers that their products were covered by consumer law for two years but under the Consumer Guarantees Act guarantees do not expire after a legally prescribed period of time.
"What is reasonable depends on the nature of the goods, any statements made about the goods and how the consumer, in fact, uses the goods," Rawlings said.
"Although businesses may form a view about how long a product should generally last, they must assess each reported fault on its own merits. They should not base decisions solely on how long a consumer has owned a product. The reasonable lifespan of a product will depend very much on what the product is."
The commission's investigation found Apple was likely to have misled consumers by trying to exclude its liability for non-Apple branded products, "when Apple is responsible, as a retailer, for compliance with the consumer guarantees applying to all products it sells, even if it is not the manufacturer".
It also looked into a complaint from a customer after three iPhone 6 Plus devices failed in three different ways and was told by an Apple representative that Apple had a policy of providing four replacements before considering an alternative remedy when the CGA contains no requirement on a set number of faults.
The commission also found Apple provided conflicting information about the availability of spare parts, repairs and misleading statements about replacement products.
"It is natural that many retailers may wish to liaise with manufacturers to assess and remedy product defects but they must not point blank refuse to address consumer complaints and refer consumers exclusively to manufacturers for attention," Rawlings said.
The commission said Apple had cooperated during its investigation.
"Apple voluntarily made changes to respond to our concerns, including making clear to its staff that consumer law rights are not time-bound," the regulator said.
"We expect Apple to consider the other issues identified in our warning and amend its practices accordingly."
