He said whether there is a case for complaints depends on a couple of factors, in particular, how popular New World's parent company Foodstuffs thought the promotion would be and whether the supply secured was reasonable to meet the anticipated popularity.
"It is one thing for New World to say the offer was available "while stocks last", but if stocks were so limited they could never last a reasonable time or meet reasonable consumer demand, there could be a bait advertising issue under the Fair Trading Act for the Commerce Commission to look into," he said.
New World could "do better", he said, and should make it clear what items are still available so people can choose to shop elsewhere if the knife they want is no longer available.
A Commerce Commission spokesperson said the two complaints it received have not been assessed and that it had not investigated the promotion.
"In general it is an offence under the Fair Trading Act to mislead consumers about the availability of products.
"We note that New World has advised consumers that knife blocks are in limited supply with most stores sold out," the spokesperson said, referring to a statement posted on New World's website on January 12.
Foodstuffs New Zealand head of corporate affairs Antoinette Laird said the promotion, which began on November 2 and ends on January 24, has been one of New World's most successful giveaways.
"New World customers across the country have redeemed 50,000 Smeg knife blocks and over a million Smeg knives since the promotion began," she said.
"New World promotions, such as Spiegelau and Smeg, have offered customers high-quality European brands that are not easily available in New Zealand, and customers are simply rewarded for buying their groceries with us as they normally would.
"We hoped the knife blocks would be popular, and despite the international data suggesting we needed much less, we purchased every knife block the supplier could produce which fortunately got us through to this week, the final week of the 12-week Smeg promotion."
A listener called Newstalk ZB's Marcus Lush on Wednesday evening, saying she had been to multiple stores looking for a 15cm meat knife to no avail.
Another listener heard the woman's plea, and emailed Lush saying she had a spare meat knife that she would be happy to send to the woman.
Meanwhile, 56 New World Smeg knife stickers are on sale on Trade Me for $70, while there is a range of Smeg knives and knife blocks on offer on the online auction site.
A Smeg knife block with three knives has a "buy now" price of $700 while another block has 71 bids with the current bid at $455.
A full set of unopened Smeg knives had a Trade Me starting price of $320.
