Food export company Oravida made a $30,000 donation to the National Party two months after Justice Minister Judith Collins' visit to their Shanghai office last year.
Electoral Commission documents show the contribution to National's war chest was received on December 23 from Oravida Group. Ms Collins visited the company during a ministerial visit in October last year.
Official documents also show the private dinner Ms Collins had with Oravida bosses and a senior Chinese official was signalled 12 days before the meal, with MFAT asked to provide a briefing for it.
Ms Collins has been under constant pressure regarding the trip, which included a visit Oravida – in which her husband is a director – and a private dinner she had with its bosses Stone Shi and Julia Xu, along with a senior Chinese border official.
A 349-page document of emails in relation to the October trip, mostly of blank pages, was released under the Official information Act today.
The email trail shows Ms Collins' senior press secretary saying on October 8 she wanted to confirm the minister's schedule in Shanghai because a private dinner was possibly being planned.
"Can we find out what the timetable in Shanghai is. Especially in the evening as Minister may attend a private dinner. Obviously the host may have arranged a dinner already but if you can feel the way on that please (sic)," the email reads.
Another email on October 15 confirms the dinner on October 20, but redacts the names of people who will be present. It requests there be a Ministry of Foreign Affairs and Trade briefing.
It says the border official "has agreed to meet with the Minister arranged by Stone Shi, Oravida (sic)" and the dinner could be at Ms Collins' hotel.
Under initial questioning from media about the trip in March, Ms Collins insisted she had dropped in at the company's Shanghai premises for a cup of tea on the way to the airport.
However, the documents show the visit had been planned days beforehand, with the trip being referred to as the "Oravida tour" in an email on October 16.
As early as October 11, MFAT was considering "how best to include these two [Mr Shi and Julia Xu] into the Minister's programme" and gave two options for a meeting – a lunch or a drink or dinner on a Sunday night at Ms Collins' hotel.
Her office advised an invitation to the lunch would be preferable to the hotel dinner and asks to keep the Sunday night free.
Labour Party MP Grant Robertson says the discovery Ms Collins’ office requested a briefing "must be the final straw" for the Prime Minister, who in the past has said the Minister was on her final warning after withholding other details of the dinner.
"For some reason the request for the briefing was later withdrawn by the Minister’s office which suddenly claimed it was a private dinner," he says.
"It is now clear this was never a private dinner. It was a minister meeting someone who could influence whether Oravida – a company her husband is a director of – got its products into the lucrative Chinese market."
While the trip was supposed to be a taxpayer-funded visit about justice issues, Ms Collins also used it to for multiple meetings to benefit her husband's company, Mr Robertson says.