A judicial review will be held in the High Court at Wellington next month into the Crown's decision to drop charges against former Pike River Mine boss Peter Whittall.
The Herald on Sunday can also reveal the Independent Police Conduct Authority is close to finishing an investigation into whether police should have re-entered the mine, where 29 miners and contractors died in an explosion on November 19, 2010.
Under the Health and Safety in Employment Act, the former Department of Labour laid 12 charges against Whittall, the mine's former boss, in relation to the mining disaster.
But the charges were dropped in December 2013 after a review by the Ministry of Business, Innovation and Employment deemed "the likelihood of obtaining a conviction was low".
Instead, Whittall and Pike River Coal offered voluntary $110,000 reparation payments to the families of the 29 dead men and also to the disaster's two survivors, Russell Smith and Daniel Rockhouse.
In what is the only piece of ongoing litigation in connection with the tragedy, a judicial review of the decision to drop the charges against Whittall will now be held in the High Court at Wellington on May 25 and 26.
The action has been taken by Anna Osborne (who lost her husband Milton in the disaster) and Sonya Rockhouse (the mother of Daniel and victim Ben). It is supported by Helen Kelly, the president of the Council of Trade Unions and other families of the Pike River 29.
"I don't believe he [Whittall] is the only one who should be charged but he was CEO at the time [of the tragedy]," Osborne said.
"The families of the 29 have had no justice. I don't know how charges concerning the deaths of 29 people can be dropped."
Kelly said it was wrong that while the Pike River tragedy had prompted health and safety law changes, no individual had been held accountable.
Meanwhile, the IPCA confirmed it has almost finished its investigation into a complaint lodged by Kelly over how police handled the failed plan to re-enter the Pike River mine.
Last November it was announced Pike River would not be re-entered, more than six months after work had begun on trying to make the mine safe for a recovery mission.
Families of the dead men had hoped re-entry would lead to the recovery of some of their loved ones' remains and uncover key evidence for the laying of potential criminal charges. Kelly said she complained because she believed police should not have relied on Solid Energy's advice that re-entry was not feasible.