Speaking at a public meeting at the Paroa Hotel in Greymouth yesterday, Mr Peters said his party believed a report that said there was no technical mining reason that re-entry could not be achieved safely.
The report, written by international mining experts and presented by the Pike families, called for the Government to take over ownership of the mine, and for a detailed re-entry plan to be developed.
"We believe your report and believe that a party should be allowed to enter the drift to look for your men,'' Mr Peters said.
"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.''
Mr Peters said re-entry need not wait until the election later this year and Prime Minister Bill English should "stop being weak'' and allow people to go into the drift.
The mine has been closed since November 2010 after a gas explosion killed 29 workers.
Labour leader Andrew Little has promised a Labour Government would get an independent assessment of the mine and re-enter it if it was declared safe.
Mr Peters said that promise was "weak and disingenuous''.
"How many more reports do the authorities need before they can say `Go in'? What more proof could they possibly want?''
The Paroa Hotel is owned by Bernie Monk, whose son Michael died in the mine. Mr Monk said a crowd of more than 100 gathered to hear from the New Zealand First leader.
"He was overwhelmingly applauded by the people here today ... he is the first politician that has really stood beside us and made his feelings known.''
Mr Monk said his understanding of what Mr Peters meant by "bottom line'' was NZ First would not go into a coalition with any party that would not commit to allowing re-entry of the drift.
"Whether people around the country realise it or not, this is becoming an election issue - it is one of the issues on the table. And I think other parties are starting to follow Winston's lead - the Green Party has seven representatives coming down to the picket line on Wednesday.''
A former miner in Australia in the 1970s, Mr Peters has said he would be willing to be among the first to enter the drift.
Prime Minister Bill English has said the safety reforms that followed a Royal Commission into the 2010 disaster meant there were strict legal requirements about painting a house, let alone entering a dangerous mine.
Pike River was the "most dangerous workplace in New Zealand'', he said, and approving a re-entry would go against the very health and safety laws passed in response to the disaster.
- By Nicholas Jones of the New Zealand Herald
