The ACT party will push John Key to change his mind on raising the pension age if it ends up helping National form the next government.
ACT leader Don Brash said the public should be asked whether the retirement age should rise from 65 to 67 by 2023.
National Party leader John Key has promised not to change the rules on superannuation and has said he would resign as Prime Minister if he did.
But Dr Brash says he strongly disagrees with Mr Key, and will try to change his stance.
Dr Brash says a referendum might get Mr Key "off a hook" as he may be able to say that his commitment on superannuation shouldn't have been made, circumstances have changed and he recognises that the public want a change.
The ACT leader says New Zealand needs to face the stark realities about its economic future and it should be up to the public to decide whether changes should be made to superannuation.
He says its inevitable that the pension age needs to rise, and the longer that's deferred, the more difficult the situation becomes.
The Labour Party said last month it would raise the age of entitlement to 67.
Under Labour's policy, the age of entitlement would rise gradually, starting in 2020 and hitting age 67 by 2033.