"[Firmin] has been the only inspector since April. They've known they have a shortage since then. They still don't have enough cover. In the meantime we've still got three to 400 guys working underground.
"There hasn't been enough action."
Mr Little said it was disturbing that miners were still inside the Huntly East coal mine when gas levels reached five per cent.
Machinery is meant to stop when gas levels reach 1.25 per cent, and full evacuations are carried out once they reach five per cent, he said.
"Part of the emerging culture in New Zealand mining is it is getting harder and harder for workers to say 'I don't feel safe'. That was part of the problem at Pike as well."
DOL has employed two new mines inspectors in the wake of the Pike River disaster and is on the lookout for a Chief Inspector.
But none of the new new staff have yet started work.
Solid Energy chief operating officer Barry Bragg earlier told Radio New Zealand the higher than usual methane levels were detected after miners struck a geological fault.
This involved removing the workers from the mine and using an auxiliary fan to ventilate the mine.
"As soon as methane in any place hits 1.25 per cent our controls kick in and we begin degassing that area of the mine," he said. "During the degassing procedure the methane got as high as 5 per cent. The explosion range is from 5 to 15 per cent."
Mr Bragg said there had also been a "non-compliance" incident involving two experienced workers during the degassing procedure, but miners' lives were not put at risk.
The incident is being investigated, he said.
It has been just over a year since a gas blast in the Pike River coal mine near Greymouth killed 29 men.
Earlier this month, Mr Firmin told the Royal Commission of Inquiry into the Pike River disaster he had been told by Huntly East mine staff not to conduct impromptu visits as they did not have the staff to take him underground.
