The families of workers who died in the Pike River coal mine are calling on former chief executive Gordon Ward to give evidence to the Pike River Royal Commission.
The inquiry into the disaster resumed on Monday in Greymouth with a focus on the company's management structures and systems before the mine exploded on 19 November, killing 29 men.
Mr Ward left his job less than two months before the fatal blast but is refusing to return from Australia for the inquiry.
Bernie Monk, the spokesman for some of the families, says all former managers have a responsibility to come back and help find out the truth.
"He should be able to come up and voice his opinion and help for future things," Mr Monk said.
Mr Ward was responsible for the Pike River mine project from the late 1990s until he resigned and is now working in the coal industry in Australia.
The commission says it asked Mr Ward to file evidence and appear in the hearings, but he declined and it cannot compel a person who is living overseas.
Some groups represented at the inquiry say Mr Ward has questions to answer and could hold vital information about the company's approach to safety.