The chairperson of the Pike River Coal has admitted failures with his board's system of safety monitoring.
A Royal Commission is being held into the disaster at the mine in which 29 men died following explosions that began on 19 November last year.
The third phase of the inquiry is focusing on safety systems at the West Coast mine before the blasts.
During more than eight hours of evidence on Wednesday, John Dow maintained that he was never told of widespread safety problems at the mine which have been revealed by a number of former workers.
They include methane gas spikes and workers bypassing safety cut-outs on machines.
Mr Dow admitted that the reporting system to the board he chaired must have failed.
Nicholas Davison, QC, a lawyer for the Pike River families, put it to Mr Dow that he should have known about serious incidents, such as workers bypassing safety devices.
"Had you known, you would have intervened in any number of ways, would you not?"
"I would have, yes," Mr Davison replied.
Mr Nicholson: "You would have known men's lives were at risk?"
Mr Dow: "I would have known and wouldn't have tolerated it."
Mr Nicholson: "So the system failed in terms of getting the information up to the board, as you see it?"
Mr Dow: "It would appear to have been the case."
However, Mr Dow told the inquiry that safety issues could easily have been raised.
Earlier, the Royal Commission was told no full risk assessment was ever done of the operating mine.
The commission's lawyer questioned why a review of the mine in 2009 recommended a broad-brush risk assessment of the mine's operations be done, but this did not happen.
A site assessment was carried out in 2005, but this was before tunnelling had begun and covered only environmental matters.
Mr Dow said a full risk assessment was planned to happen after hydro-mining reached full production in 2011.