National must hope specials fail Greens

National's faint hope of gaining the Treasury benches rests on the Greens failing to make the 5 per cent threshold when the count of special votes is announced on October 1.

But the Greens' share of special votes would have to collapse spectacularly for that to happen.

And even if the Greens disappeared, Labour would still be the party with the most seats and New Zealand First and United Future would have to u-turn on their previous commitment to dealing with the biggest party.

The Greens' share of special votes has increased in the last two elections - in 1999 it got 8.07 per cent of the special votes and in 2002 11.7 per cent.

The party has calculated that for it to drop back below the 5 per cent threshold - which would make it disappear from Parliament - its share of special votes would have to fall below 4.45 per cent.

That means it would have to get fewer than 9696 of the 218,000 specials.

In both the previous elections, specials gained it another MP, and it hopes the same will happen again and Nandor Tanczos will be returned.

The election-night result gave the Greens 5.07 per cent support, which would need to rise to 5.32 per cent for Mr Tanczos to come back. This is equivalent to getting 17,190 of the 218,000 specials.

If the Greens were knocked out of Parliament by falling below the threshold, and assuming the other party vote proportions were the same, Labour would get two more seats and rise to 52, National would gain two to 51, and Jim Anderton's Progressives would get another seat, giving them two.

Parliament's overhang would also reduce by one to 121.

Labour would still have more seats, meaning that, given NZ First's and United Future's commitment to talk with the biggest party on confidence and supply, little would change.

Greens co-leader Rod Donald said the party would have to get an appallingly low percentage of the special votes to fall below the threshold and he was "99.9 per cent sure" it would be back with at least six MPs.

He said National was "typically desperate" to hope for the Green Party's demise.

"But one has to be careful not to be over-confident, so we are patiently waiting."

Labour has a slender 22,751-strong party vote lead over National, but National is unlikely to overtake it because National was allocated the 120th MP under the MMP system and it would be the first to lose an MP if the Greens or another party, possibly the Progressives, gained one once specials are counted.