Winston Peters says if anything goes wrong during any Pike River mine re-entry, he'll make sure no one is held criminally responsible.
But he won't make the same promise for those "who were guilty in the first place" of allowing the mine to become so dangerous.
Twenty-nine men lost their lives in the 2010 tragedy, and no one has been held criminally responsible.
The New Zealand First leader has previously said he'd be willing to go into the mine himself, if that's what it took to retrieve the bodies.
"I'm prepared to go in myself - not as a boast as some in the media say, but as an indication of my confidence safe re-entry is possible," he told The Nation on Saturday.
"I've worked 11 miles underground in a mine. I know a bit about the dangers… We can take away any possibility that by making a decision to give the miners' families justice, anyone else would be, for that event, capable of some sort of penalty. We can remove all that."
Going by the latest polls, his party could decide whether National or the Labour-Green bloc forms the next Government. Mr Peters is convinced Labour and Greens would be willing to give any Pike River re-entry exemption from prosecution under existing health and safety laws, should something go wrong.
"They will now, because they have been embarrassed into taking action."
Prime Minister Bill English has suggested if Mr Peters is so sure it's safe to go back in, he should "become a director of a company and take legal responsibility".
"In the end there's no way of avoiding legal responsibility for the safety of anyone who goes in the mine or might go in the mine," Mr English said in January. "Our law allows for prosecution of people making a decision to do something that looks dangerous even before it is done."
Mr Peters appeared to reject Mr English's suggestion on The Nation, without actually ruling it out.
"I'm not going to have a duel of wits with an unarmed opponent on this matter, like Bill English. His behaviour has been repugnant, and so has John Key's."
Footage of men and a robot in the mine from March 2011 was leaked to Newshub last week.