The New South Wales Government has admitted it may have accidentally approved logging in old-growth forests for years.

A report, commissioned by the Department of Environment, Climate Change and Water and carried out by Aerial Acquisitions, says the mistake was caused by inaccurate surveying.

''The implementation of old-growth is highly variable and problematic and has apparently resulted in some areas of old-growth being potentially available for harvest,'' it says.

The report recommends that the department do more field work, start a peer-review process so that surveys can be checked, and use better digital monitoring equipment.

The department conceded the findings in the report were correct, and it said it would follow all the recommendations, including upgrading technology.

The director of landscapes and ecosystems conservation, Tom Grosskopf, told the Sydney Morning Herald: "We are instituting an immediate strengthening of the application of the protocols for assessing old growth forests, and the department intends to increase resources for fieldwork needed to confirm the presence of old growth forests.”

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