Australian police say they won't pursue criminal charges against a former Hobart school teacher, who's been named as a child sex offender and who now lives in New Zealand.

Ronald Thomas was named publicly during a royal commission as having abused students in the 1960s - because police thought he was dead.

He's actually been living in Manawatu for decades and has retired from his music teaching career - he strongly denies doing anything wrong.

Police assistant commissioner Donna Adams says officers visited New Zealand to question the now 77-year-old who denies the allegations.

They now accept that on the available evidence, there's unlikely to be a reasonable prospect of conviction. His former students have been informed.