In a letter detailing the apology he will give, which was delivered to the families of the 29 men last week, Mr Key said he "deeply regretted" the loss of life and suffering caused by the mine explosion.
The Prime Minister's apology comes a month after the release of the Royal Commission of Inquiry report on what caused the explosions at the West Coast mine in November 2010.
In his letter Mr Key said he hoped the report, which highlighted corporate and regulatory failures, gave the families some answers and gave them some closure.
"On behalf of the Government, I want to reiterate my apology to the families, friends and loved ones of the deceased men for the role this lack of regulatory effectiveness played in the tragedy," he wrote.
Neville Rockhouse, the mine's former health and safety manager whose son Ben died in the disaster, warned Mr Key would be walking into a "hornet's nest" when he met the families.
Mr Key had backed away from a body recovery plan which he had previously committed to, Mr Rockhouse told National Radio today.
Recovering the bodies was dependent on the drift (main tunnel) being reclaimed.
"We would love John Key to agree to that today but we doubt very much that that will happen. It would be great if he walked in there and said he was prepared to sign off a tunnel reclamation project," he said.
If these efforts proved it "was beyond all hope getting any further into that mine" then the families would take steps to turn the area into a burial site, he said.
The Government yesterday released its plan to implement all 16 mine safety recommendations made by the royal commission, and has said it will move as quickly as possible to implement them.
Economic Development Minister Steven Joyce, acting Labour Minister Christopher Finlayson and Energy and Resources Minister Phil Heatley will oversee the recommendations, aimed at addressing systemic failures in the health and safety regulatory regime.
"We owe it to the families of the victims of Pike River to ensure we follow through promptly on every recommendation the Royal Commission has made," said Mr Joyce yesterday.
A new independent regulator will advise the Government on several key recommendations and it is due to report back on New Zealand's entire workplace health by April next year.
The changes will also address the recommendations for worker participation in mining health and safety management, more detailed health and safety management responsibilities for company directors, and statutory mine managers, management training and emergency management planning.
The complete response to all recommendations is due to be completed by the end of next year.
Mr Rockhouse was supportive of the Government's implementation plan, saying the legislative changes would be part of the Pike 29's legacy.
- APNZ and Greymouth Star
