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.
While the two parties had a "general discussion" a while ago "we haven't requested any specific arrangements".
"I'm not going to say what discussions took place or if we would or would not like them to stand in certain seats. But we haven't reached any conclusions about any of these matters."
Asked about the three seats in question, he said National did have strategic seats "but we are not seeking accommodations from Act for our strategic seats'.'
Dr Brash said he did not want to confirm details of National's request, but failing to stand candidates in too many seats could be detrimental to Act's party vote campaign.
"We are primarily focused on the party vote in every electorate except Epsom. The advantage [of standing candidates] is you have someone to wave the flag for the party. That's why we are not looking at doing a number of these deals."
He said Auckland Central MP Nikki Kaye was capable and he was confident she would hold the seat for National without Act help.
Ms Kaye won Auckland Central from Labour's Judith Tizard by 1497 votes in 2008 - but Labour's new candidate, Jacinda Ardern, is considered a greater threat.
In Waimakariri - held by Labour's Clayton Cosgrove in 2008 by 390 votes - Act's candidate got 1717 votes. Although Act plans to stand, it is likely put forward a lower-profile local candidate than in 2008, when Aaron Keown campaigned relatively strongly.
Dr Brash said a number of individual MPs had approached Act to request it not to stand in their electorates. All were rebuffed, although Dr Brash said it was obvious the electorate vote was irrelevant to Act in all seats other than Epsom.
In previous elections Act has not stood in about five electorates, but that was because the party either could not find the right candidate or did not deem it worthwhile.