The Department of Conservation says it could have done more to prevent the disappearance of a volunteer who went missing on Raoul Island in the Kermadecs earlier this year.

Mihai Muncus-Nagy, from Romania, went missing while taking temperature measurements from Fishing Rock on Raoul Island, 1000 kilometres north east of Tauranga, on January 2.

A Department of Conservation volunteer went missing while taking water temperatures on Raoul Island in January. His body has never been found.

DOC has admitted a charge under health and safety legislation of failing to take all practicable steps to ensure his safety.

Deputy Director General, Operations Sue Cosford says at the time of the incident DOC had clear procedures in place to identify hazards and provide safety training for all staff, including volunteers, working on the island.

However she says the department acknowledges there were extra steps DOC could have taken to improve safety for those working on Fishing Rock.

Sue says DOC has apologised directly to Mr Muncus-Nagy's widow and parents following the tragedy.

She says DOC has reviewed and strengthened its health and safety procedures on Raoul Island.

DOC has stopped manually measuring the sea temperature at Fishing Rock, following the incident, and is investigating gathering the data using automated sensors.