An audit of Oceana Gold's environmental monitoring data has shown inconsistencies, inaccuracies and failures, the Otago Regional Council says.
However, Oceana Gold says it has never had a compliance issue with the regional council and the issues concerned how it reported its data.
A report to the council's regulatory committee recently said the audit of consent conditions data related to monitoring from January 2008 to December 2010.
That information was in a report to a recent committee meeting which showed the results submitted quarterly to have varied in consistency and accuracy of sampling, requisite parameters and locations.
"There appears to be inconsistences within sampling routines, often resulting in monitoring falling well outside of the required timeframe or lacking inclusion altogether."
Major areas of concern were the lack of consistent or full annual sampling programmes for surface water and the inaccuracies or inaccurate nature of a number of groundwater monitoring sites, the report said.
"A further area requiring attention is the reporting to the consent authority of exceedences or failures during regular monitoring programmes."
Improvements would be necessary to ensure more real-time information was readily available and reported, it said.
Oceana Gold Corporation chief operating officer Mark Cadzow said the company had provided the council with huge volumes of data quarterly for 12 years and had never had a compliance issue.
It had meetings with the council about the "nature" of its reporting and believed it was about "both the council and us moving into the electronic age".
"This is the first time we've had any feedback at all about our reporting."
Many issues had simple explanations, such as streams not always flowing, Mr Cadzow said.
If there were anything that needed to be changed around its monitoring then it should be addressed during the company's next round of resource consent reviews, he said.
