Seeka Kiwifruit Industries, the only major Bay of Plenty kiwifruit packhouse not included in last week's letter to parliamentarians, has written to Prime Minister John Key adding its support for Zespri.

Seeka CEO Michael Franks says the omission of the company's name from a letter signed by 15 other post-harvest companies was a mistake and not a deliberate decision not to support Zespri.

Seeka has written to the Prime Minister to express support for Zespri.

'There was an initial discussion and we waited to see the draft. Once we realised we had been omitted – we rectified with a letter of support of our own,” he told SunLive.

The letters follow a court case regarding customs duty in the China market which resulted in Zespri's former China agent Liu Xiongjie being arrested on smuggling charges, ordered to repay $7.6m in underpaid customs duties on New Zealand kiwifruit and sentenced to 13 years jail.

Michael's letter to John Key echoes that of the earlier letter, saying the current speculation and campaigning against Zespri will do more to damage the Zespri brand, pack house and grower interests than the customs matter itself.

Seeka represents approximately 25 per cent of the kiwifruit industry 'and this united with the pan industry letter provides you with a united view.

Michael says Seeka continues to support Zespri and the kiwifruit industry structure.

Liu Xiongjie is appealing his conviction with his lawyers saying he only played a minor role in the customs case. At the same time in New Zealand the ACT Party is calling for an inquiry into Zespri and Labour wants the company called before the parliamentary primary production select committee to answer MPs' questions.

Zespri chairman Peter McBride has written to growers saying 'it is important that growers have the facts of the situation”.

'It is true that Zespri had questions about the basis of the dual invoicing process. Concerns were raised by some employees and we did take actions at the time to check that the process was appropriate.

'In hindsight we should have checked more rigorously and we have clearly identified that our compliance systems need to be strengthened.

'Claims that Zespri knew what was happening are wrong. Zespri was led to believe by its former importer that an agreement with China Customs to allow for dual invoicing did exist, and that appropriate duties were being paid. All Zespri's actions at the time with regard to the import of kiwifruit into China were conducted in the context of believing such an agreement did exist,” the letter says.