Act has dug in its heels in election strategy talks with National, knocking back two requests for deals in electorate seats.
Party leader Don Brash confirmed that under an "informal understanding" Act would not stand in the marginal seat of New Plymouth to enhance National candidate Jonathan Young's chances of holding the seat.
However, Act had not agreed to a similar arrangement in any other seat.
It is understood National asked Act not to stand in three seats: New Plymouth, Waimakariri and Auckland Central. In return National will again give the nod to its voters in Epsom to elect Act's candidate, John Banks, to ensure Act returns to Parliament.
National Party president Peter Goodfellow said it was Act's choice not to stand in New Plymouth, but in his opinion there was no "arrangement" as such.