Mr Brown says the move is bound to hurt sales revenues, as the price will also halve, but it is the right thing to do to maintain consumer trust amid growing debate over the marketing of sugary treats to children.

"We sell 13.5 million Killer Pythons a year - when we halve the size we'd expect at least a 20 per cent volume loss as a result," he said. "People may buy more of the smaller products but not enough to make up for the loss in weight," he said.

"But companies that are trusted tend to be rewarded down the line - we want to be the leader in nutrition, health and wellness, so we need to have products that are right-sized to play a role in healthy diet," he said.

Nestle is the leader in the $1.5 billion Australian confectionery manufacturing industry, according to IBISWorld, with 23 per cent of the market for treats such as hard and soft candies and mints. In the chocolate market, which is worth another $1.5 billion, Nestle has about 15 per cent market share.

While confectionery volumes are rising, industry revenue has fallen 0.1 per cent a year over the past five years due to price deflation and a consumer shift away from sugary treats to healthier products such as nuts and dried fruit and low-sugar alternatives.