The former safety manager at Pike River Coal says he became aware of some unsafe practices occurring underground only after deadly explosions at the mine.
A Royal Commission is being held in Greymouth into the deaths of 29 men killed in a series of explosions at the West Coast mine from 19 November last year. The mining company went into receivership in December.
Neville Rockhouse, who lost a son, Ben, in the mine has been giving evidence this week.
In emotional testimony on Thursday, Mr Rockhouse said another son Daniel, who was one of only two men to survive the initial blast, later told him about unsafe practices and said he had not told his father earlier because he did not want to ruin his career.
"I said bugger my career - go to the cops and tell the truth, just tell everything that you know. Otherwise we don't learn from it, otherwise I've lost a son, you've lost a brother and 28 families have lost people."
He said he had been frustrated over safety issues at the mine and was ready to resign until Doug White was appointed general manager in January 2010.
Earlier, Neville Rockhouse held back tears as he recalled realising that his son Ben was still underground on the day of the first explosion.
Mr Rockhouse said attended an emergency meeting late in the afternoon and it was then he realised the seriousness of his youngest son still being in the mine.
He told the hearing he sat in stunned silence, thinking about him and how he had been due home that evening.