New Zealand's potato trade is struggling as exports to some key markets plummeted in December, new figures show.

The data shows fry exports were back nearly 40 per cent in December compared to the same month a year earlier.

Sales to the Philippines were down 77 per cent and exports to New Zealand's largest customer, Australia, were down nearly 50 per cent.

Last year, a dispute broke out over claims European producers were dumping frozen fries into markets around the world.

Potatoes New Zealand chief executive Chris Claridge believes that is a major factor in the drop in export.

"We can see increased numbers of European fries into markets we normally supply, that's because they have to go somewhere.

"Europe traditionally exported about 400,000 metric tonnes of frozen fries and to put that into context, New Zealand's total annual exports is the equivalent of two weeks of European exports.

"So they have the ability to swamp markets."

Chris says the effects of COVID-19 on hospitality sectors around the world also affected the drop in exports.

Despite the drop in some markets, Thailand showed plenty of interest in New Zealand potatoes in December, up more than 60 per cent on the same time in 2019.

Chris says New Zealand has a good reputation for frozen fries and some buyers respected that.

"New Zealand frozen fries are of a world standard and generally buyers will stick with their existing suppliers and not swap out on the basis of price."

Chris believes there was also dumping in the domestic market, and says that was why the industry took the matter to the Ministry of Business, Innovation and Employment for investigation.

That got under way in late October, and he says the ministry's work is progressing.

"Let me make it clear, as an industry, we absolutely support free trade but free trade doesn't mean no rules and we are looking to stabilise and secure our domestic market."

Riley Kennedy /RNZ.