Cory Bernardi's fledgling Australian Conservatives party could be the decisive factor in the tense byelection in Batman, the party leader said on Wednesday.

Senator Bernardi said he believed there were enough conservative voters in the electorate in Melbourne's north and inner-north to give his candidate Kevin Bailey a good showing in the March 17 poll.

Liberal preferences got Labor over the line in a tight race against the Greens in the seat in the 2016 federal election, but the Liberals have decided not to contest the byelection in a move that was seen as a boost for Greens candidate Alex Bhathal.

Australian Conservatives Leader Cory Bernardi.

Senator Bernardi told Fairfax on Wednesday that no final decisions had been made about where his party's preferences would be directed but it would be "extraordinary" if the Greens were put anywhere other than last on Australian Conservative how-to-vote cards.