ACT may opt to sit on the cross benches and support the Government from there rather than taking any ministerial roles following November's election, party leader Don Brash says.
If National won the election and the two parties could not meet on common ground ACT may not sign up to the same support deal currently being used, Dr Brash told TV3 political show the Nation.
Former ACT leader Rodney Hide is a minister, and other party MPs were in the past.
Dr Brash said ACT would wait and what happened after the November 26 general election.
''The reason is, frankly, we don't know what the electoral landscape will look like. It may well be that the ACT Party decides not to formally join the government at all, but to sit on the cross benches, but supporting a National Party government.''
However, he ruled out supporting any of the left-leaning parties.
''National's our first preference without question but we may feel there's not enough common ground after the election to actually form a formal coalition.''
However Dr Brash declined to say if he had any bottom lines such as ditching the emissions trading scheme that ACT vehemently opposes.
The party would like to see minimum youth rates reintroduced; National is considering options on the issue but has not publicly stated a position.
''We've got to weigh up those things when the post election bargaining takes place.''
Dr Brash also defended doing a deal with National where its candidate, Paul Goldsmith, will campaign for the party but not the electoral vote in Epsom. The seat is held by Mr Hide and candidate John Banks will stand in November for the party.
On Friday National also confirmed it was going for the party vote only in Ohariu, leaving the way clear for support partner Peter Dunne.
Dr Brash said there was nothing wrong with such arrangements and they were part of MMP.
''It may make sense in isolated cases to work together in particular electorates.''
It has been reported that deals had also been done with National whereby Act would not stand candidates in the marginal seats of Waimakariri, held by Labour's Clayton Cosgrove, and New Plymouth, which Labour's Andrew Little will try to lift from National's Jonathan Young.
The possibility of as many as eight other seats being negotiated has also been reported.
Dr Brash said ''there may be isolated cases where that might be the case'' but denied there was a wider plan on to work together across a number of electorates, saying the idea was ''absolute nonsense''.
Is it a good decision to lower the alcohol limit for driving?Related story: Alcohol limits to be lowered