Mr Whittall, testifying to the inquiry into a series of explosions at the West Coast mine last November which left 29 workers dead, said he did not think a new and improved inspectorate would have changed events leading up to the explosion, as the cause of the explosion had not been established.
"But I do agree there needs to be a significant review of the role of inspectors in New Zealand," he said.
Mine inspectors were proactive at Pike River, given their limited resources, with eight inspections and 123 interactions with inspectors at the mine last year, Mr Whittall said.
Earlier yesterday, counsel for the Royal Commission of Inquiry, Simon Mount, referred Mr Whittall to a report by gas drainage specialist Miles Brown.
The report found various safety issues, including that the gas drainage pipeline was of an inadequate diameter and the workforce had insufficient knowledge of the risks of gas holes in pipelines.
Management of gas was of "great concern" and no outburst threshold had been set for the mine.
Mr Mount asked Mr Whittall whether the mine's gas drainage pipeline had been upgraded from 10cm to 25-30.5cm in diameter, as recommended in previous reports.
Mr Whittall said it had not been upgraded, but that the issue was being addressed before the explosions.
Mr Mount also referred Mr Whittall to a company report to the Department of Conservation which said the mine's ventilation shaft was inappropriate as a second exit point.
Mr Whittall agreed it was not appropriate as a permanent second exit and said the ventilation shaft was meant only as a temporary exit until another was built in another area as the mine was developed.
Earlier yesterday, Mr Whittall said he was not aware of a proposal for the West Coast mine to have two exits.
"No-one ever had that discussion with me," he said.
When he started work with Pike River, the approved initial design had always involved a single tunnel and ventilation shaft.
In the 2005 plans, a second exit was planned to the west of the mine but construction had not begun at the time of the explosion.
