Cadbury is cutting the size of its chocolate blocks, citing manufacturing costs and a preference not to increase the price.
The move has been described as a case of less costing more by the country's leading consumer watchdog.
New chief executive Jacqueline Evison said the move would see the 220g family block drop by around 10 per cent to 200g - the equivalent of a row of chocolate.
"We didn't take the decision lightly by any stretch," Evison said. "We've been concerned about our rising manufacturing costs for a while now and we can't continue to absorb those costs so obviously what you do is you look at what the feasible options are."
Evison said the choice between increasing the price or reducing block size had been difficult but she felt the firm had made the right decision.
"We've got a tough year ahead of us, New Zealand is a highly competitive market and business is tough," she said. "We had a choice to make about whether we increased the price we recommended to our retailers or reduced the size of the block and we've taken the choice to reduce the size of the block to make sure it stays an affordable treat.
"We love the fact that people love our chocolate and we know that people are going to be disappointed that there's less chocolate to go around, but we wanted to be proactive and make sure we got out well ahead of the change."
In early 2009, the company cut its 250g and 150g blocks by around 20 per cent, before increasing the size again slightly after market backlash.
Consumer New Zealand said by selling the smaller-sized blocks, Cadbury was effectively raising the price.
"It's one occasion where less costs more," Consumer chief executive Sue Chetwin said.
"It just seems to be a continuum ... They swapped their butter for palm oil then went back [and] then they had the size issue."