New Zealand First leader Winston Peters is misleading Pike River families by telling them the decision not to re-enter the mine is political, Prime Minister Bill English said.

Mr Peters met with families of the 29 men who were killed in the 2010 mining disaster at the mine gate on Saturday and at a public meeting in Greymouth on Sunday.

The families want the drift at the entrance of the West Coast mine to be entered in the hope of retrieving bodies or evidence about the disaster, but government- owned miner Solid Energy said it's unsafe and is permanently sealing the mine.

In December Mr Peters, who was a miner in Australia, met with families outside parliament and volunteered to be one of the first to enter.

Mr Peters said the families have internationally respected advice declaring the drift is safe to enter, contrary to Solid Energy reports which indicate methane at deadly levels.

"We believe your report and believe that a party should be allowed to enter the drift to look for your men," Mr Peters told families.

"And to all those who say we're not serious on this promise we say our party will make re-entry into Pike River a bottom-line at the next election, whenever that is."

Mr Peters has vowed the issue will be non-negotiatble in any coalition discussions.

Mr English maintains the decision not to re-enter the drift is one of safety and must comply with laws that were strengthened in the wake of the Pike River disaster.

"Any decision to go in there has to comply with that law. Mr Peters is misleading the families if he's telling them it's a political decision," he said from London.

"If he's willing to become a director of a company and take legal responsibility then I'd take him a bit more seriously."