Foreign-owned companies have secured approximately $100 million in government education contracts over the past two years, with local publishers arguing they faced unfair competition in the procurement process.

Four companies won education ministry contracts for mathematics resources and training materials, all of which are either foreign-owned or distribute products originally developed overseas. The Publishers Association has published an open letter warning about cultural and national interest issues.

Local education publishing firms generated over $37 million last year, with nearly $22 million from domestic sales of locally-made products and $11 million from exports.

Andrea Tamatea, education councillor for the Publishers Association and representative of Learnwell, said domestic firms felt they did not have a fair opportunity in the procurement process. "No individual publisher wanted to be seen as having a grumble because they missed out but I think it's the unfairness," she said. "Has this government followed the procurement process correctly and if they have, it just feels as if the outcome was pre-determined."

Tamatea said offshore companies had an advantage because the new curriculums resembled Australian and English curriculums they already served. "The criteria had been specifically catered for what they already had on the market," she said.

She said schools stopped buying local products because the government was providing maths resources to support the new curriculum, with at least one company losing nearly all its primary school sales.

The Education Ministry said it followed government procurement rules requiring equal treatment of all suppliers regardless of ownership. "Contracts are awarded to those that best meet the specific requirements and offer the strongest mix of quality, delivery, and price," a ministry spokesperson said.

The ministry said one winning supplier is New Zealand-owned, one is Australian-owned with a New Zealand team, and two are internationally owned. All four employed New Zealand-based authors and teams alongside international expertise, it said. The New Zealand-owned winner is a distributor of foreign-developed products rather than a publisher.

Education publisher Dame Wendy Pye said the government's decisions contradicted its policy of supporting New Zealand companies. "In my experience never has any of this sort of money been dropped for resources. Never ever ever," she said. "We're talking about huge amounts of taxpayer money so I think some of it should go to New Zealanders."

Dame Wendy said her books are rated highly in other countries and overseas resources are not necessarily superior.

Adrian Keane, director of publisher Edify, said three companies that won contracts last year had won a closed tender a year earlier, giving them an advantage. "Being chosen in the first closed tender gave them a substantial advantage over other potential participants because they'll have had a lot of time with their products in the market, they'll have had time communicating with the ministry to hone their resources and ensure they are as close to curriculum outcomes that the ministry is looking for," he said.

Keane said the situation felt like "running a 100-metre race against opponents who are starting on the 50-metre line".

He said while returns in the small New Zealand market are not huge, national-scale contracts offer substantially more money for publishers. The tender represented an opportunity for the ministry to work with local publishers to develop resources for the structured methodology, he said.