A coroner says a health authority investigation into the death of well-known shearer Koro Mullins "obfuscated the search for truth"

The Dannevirke man died in Wellington Hospital in September, 2019 after a fatal injection of air into one of his arteries at the start of a stent surgery.

Staff promised a full investigation to Mullins' family - but an inquest has found that did not eventuate.

Deputy chief coroner Brigitte Windley has found Capital and Coast District Health Board's conduct was unhelpful - and added trauma to the whanau.

Now integrated into Te Whatu Ora, the health agency says it acknowledges the shortcomings of the review process - and has implemented changes.