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Further prosecution of Whittall not likely.
Whittall unemployed since mine disaster.
Asked about the offer of money - which amounts to $110,000 per family - Mr Key said his initial reaction was that it may look bad.
"When I first heard, which was last Sunday, that that was the action that the regulator was taking, I also thought, 'that doesn't actually look terribly good'. But on the other side of the coin, I guess the decision that the regulator has made and the judge has made, is that's the appropriate next step," he said.
"I mean no amount of money, whether it's the tens of millions of dollars of ACC payments or the essential compensation that's gone through this clause, or the money that was raised by New Zealanders through the trust funds that were established, will ever bring back those brave men.
"I think for those families, they continue to suffer because this has been a huge loss for them and it's a very long and drawn out issue, and I wish they could get closure. It's very difficult, and one of the reasons the Government has funded the ability to go up the drift is to try and give them as much closure as we possible can."
Mr Key said the families of the men would be "extremely disappointed" by the court's decision, but going through a long court process, which could take years, to end up with Mr Whittall being found not guilty would be even more "heartbreaking".
"The independent regulator has made a call that it was very unlikely a prosecution would be successful, and that's essentially the words the judge has also said," he said.
"I think that they will be hurting as a result of that decision, but there's really fundamentally nothing that I can do. It's quite inappropriate for me to try and jump into something the prosecution, a judge and independent regulator have decided wouldn't be successful."
Mr Key said a judicial review of the decision would be unlikely.