Prime Minister Bill English says Winston Peters' plan to change health and safety laws to allow manned re-entry into Pike River could put lives in danger for the sake of politics.
He says National has no plans to change health and safety laws, as Mr Peters has suggested should happen.
Mr Peters told The Nation on Saturday that any re-entry mission should be given exemption from prosecution should something go wrong.
Speaking on The AM Show on Monday, Mr English continued to defend the Government's reluctance to allow manned entry to the mine, where 29 people lost their lives in a 2010 explosion.
"What rules it out isn't a political decision," he said. "It is the fact that the assessment by people who are responsible says that it's dangerous."
Mr English would still not rule out agreeing to manned entry as a part of post-election coalition talks, but said "we're certainly not planning on changing the law to satisfy Winston Peters".
"It could be putting a significant number of lives in danger...and doing so for the worst of reasons - and that's political reasons.
"You can't have no-one responsible."
The Prime Minister said both New Zealand First leader Mr Peters and the Labour Party were misleading families into believing "that somehow a bunch of politicians are the right people to make this kind of decision, and that somehow it's safe not dangerous. That is irresponsible."
He said unmanned re-entry remained the safest way to answer the families' questions.
Mr Peters on Saturday reiterated his willingness to go into the mine himself to retrieve the miners' bodies.
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.
"[It's] 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.
"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."
Footage of men and a robot in the mine from March 2011 was leaked to Newshub last week.
Newshub.
