Winston Peters has categorically said New Zealand First will never support National's plan to raise the retirement age to 67.
"We are categorically not going to support this legislation," he said.
It deals a major blow to Prime Minister Bill English's plan to raise the age of superannuation from 65 to 67 in 2037, because polling shows National will likely need Mr Peters' support.
Mr Peters was asked repeatedly to give New Zealand First's position on whether it would support the legislation, which National intends to introduce next year.
"Can I say it one more time? We are not going to vote for this betrayal of the electorate," he replied.