The explosion at the mine was in part a consequence of the repealing of NZ’s Coal Mines Act, Hughes told the Royal Commission of Inquiry into Pike River.

"The explosion of the Pike River mine on the 19th of November 2010 had its origins in the repealing of the Coal Mines Act and Regulations in 1993,” he said.

"The mines inspectorate changed from being an active and expert participant in coal mine safety to a reactive and substantially less well qualified organisation. It became an ambulance at the bottom of the cliff not a fence at the top."

From 1999 onwards the attendance of inspectors at coal mines significantly dropped and many qualified inspectors left the industry, while those that remained visited mines less frequently, he reportedly said.

Expert witness and geologist Jane Newman of Newman Energy Research revealed her fears about the Pike River mine while explaining to the inquiry its geological structure and composition, according to One News.

"It was just my feeling at that stage that things were converging on a situation I wasn't comfortable with," she reportedly said when asked about her views about the safety of the mine.

The presence of sandstone within the coal seam could be misidentified by the drillers as ground rock, she reportedly said.

A phase two study into the complexity of the mine was not undertaken because she believed that the Pike River management seemed "busy" and it was difficult getting their attention, the court heard.

"I think, in addition, resources were starting to be tight – financial resources – and my feeling is, that is why phase two never got under way," she said.

The inquiry also heard Newman's concerns about the change of chief executive of Pike River Coal, which is now in receivership by PriceWaterhouseCoopers.

She said when she heard that Peter Whittall, who held the position of general manager mines and was considered to be safety conscious, had taken over as chief executive in September 2010, she became concerned that there would be no one on site to deal with safety and operational matters.

"Now that Mr Whittall was off-site, who was the person onsite?" she said.

Newman said she and other researchers had expressed concern in 2001 about the adequacy of some of the data about the Pike River site.

Twelve witnesses will be heard during the first phase of the inquiry, which will set out to give the overall context to the regulatory environment the Pike River Mine that was operating in at the time of the tragedy in November last year.