Prime Minister John Key was bailed up by an Act Party member angry that National was not sticking to its side of a "deal" between the two parties.
Morris Hey, Act's electorate chair in New Plymouth, approached Mr Key at a New Plymouth mall today.
He said Act had agreed not to stand in New Plymouth to help National hold the seat.
However National was failing to do its part by withdrawing its candidate from Epsom.
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Mr Key told Mr Hey to talk to his own party about the issue, and quickly moved on.
Mr Hey said it had left Act without any platform to campaign in New Plymouth and he had nobody to vote for.
"I'm not voting for National."
He believed National should still withdraw Paul Goldsmith from Epsom.
Act is not standing in several marginal electorates - including West Coast Tasman, Waimakariri and New Plymouth - under a quiet deal with National.
Mr Key has said National was campaigning for the party vote only in Epsom - which is Act's lifeline to Parliament as it struggles in the polls.
However he is yet to give a stronger indication to National voters to vote for Mr Banks, saying it "depends if I'm thirsty" on whether he would have a cup of tea with Banks.