Close to 10,000 emails relating to the controversial export of swamp kauri must be released to an environmental group after a court ruling.
The Northland Environmental Protection Society is taking a judicial review case against the Ministry of Primary Industries (MPI), alleging the agency breached the Forests Act by allowing the export of ancient kauri.
The 9700 emails detailing exports were sought by the group under the discovery pre-review phase, but MPI refused to hand them over.
Now, a High Court has ruled the emails must be released.
That has been welcomed by Green Party primary industries spokeswoman Eugenie Sage.
"What has MPI got to hide that it sought to block the release of emails and information about swamp kauri, all the while saying everything was under control," Ms Sage asked.
An MPI spokesman said the order to release the emails would be fully complied with.
"MPI will work closely with Crown Law to fulfil this discovery order and ensure that all the information required in order for the case to progress is provided by the date given.
"As this case is still proceeding, MPI is unable to comment further until its completion."
The Government moved to strengthen the oversight of swamp kauri extraction and export last July after heavy criticism by opposition parties and conservation groups.
Allegations included officials turning a blind eye to dubious export practices, and ecologically-sensitive wetlands being wrecked in the "black gold" rush.
Changes included requiring operators to notify 100 per cent of all finished products for export approval, which MPI would inspect.
Figures released to the Herald under the Official Information Act revealed exports had jumped by more than 2500 per cent in five years.
In 2009, 173 cubic metres of swamp kauri was legally exported. That increased to 1150 cubic metres in 2013, before sky-rocketing to 4356 cubic metres in 2014.
One company, Silver Fern Resource Trading, sent 1810 cubic metres in 2014 - all to China.
The Forests Act 1949 bans the export of swamp kauri logs, many of which are tens of thousands of years old, unless they are made into finished timber products.
Whole or sawn salvaged swamp kauri stumps or roots can be exported with a Ministry of Agriculture and Forestry milling statement and export approval.
The vast majority of exports are of products approved as finished such as tables, or raw stump material.
Opponents of the trade, including the Far North Protection Society, say exporters are skirting the ban by labelling kauri slabs as table tops, or superficially carving the logs and calling them artworks.