Bunnings is facing 45 charges of misleading the public over its tagline "lowest price guaranteed" promise.
The Commerce Commission, which laid the charges, says in the court documents a number of its slogans were liable to mislead the public into thinking the DIY chain's prices were the lowest on the market "when they were not".
The charges were laid by the consumer watchdog in December.
The alleged offending took place between June 2014 and February last year and involved print, radio and television marketing campaigns, in-store signs, staff uniforms as well as its website.
Some of the taglines named by the Commission as being "false or misleading" were:
• "Lowest prices are just the beginning ..."
• "Bunnings has the lowest price on everything you need."
• "Everything is at the lowest price guaranteed."
• "We've got the widest range and the lowest prices."
Each of the 45 offences is punishable by a fine of up to $600,000.
Jacqui Coombes, Bunnings general manager NZ, said the company was "disappointed" with the Commission's decision to file charges.
"We disagree with the Commerce Commission's view of our lowest prices policy and will defend our highly competitive price guarantee. We would like to reassure customers that we will continue our lowest prices policy along with our comprehensive business processes and procedures operating behind the scenes to back this up.
"We remain absolutely committed to creating more value for New Zealand consumers and believe in the right of all businesses to compete on price."
A spokesman for the Commerce Commission said he was not able to comment on the case.
On Friday, Nurofen's distributor was slapped with a $1.08 million fine for misleading the public about targeted pain relief.
The drug giant Reckitt Benckiser New Zealand was sentenced at the Auckland District Court for 10 charges laid under the Fair Trading Act. The company admitted the charges.
The offending related to the packaging and promotion of four pain-specific products - Nurofen Migraine Pain, Nurofen Tension Headache, Nurofen Period Pain and Nurofen Back Pain - which were ruled to be misleading.