Labour leader Helen Clark says the National Party still does not understand the MMP electoral system, and this will cost it.
National leader John Key earlier raised the spectre of Labour leading a "five-headed monster", if it forms the next government with the support of four parties.
His comments came before United Future leader Peter Dunne announced on Sunday 26 October that he would not work with a Labour-led government post-election.
Miss Clark dismissed the statement as ridiculous, saying Mr Key really does not have a lot of friends.
She says the National Party is definitely rattled and does not understand the importance of working with other parties
Labour currently governs with the support of three other parties; the Progressives, United Future and New Zealand First. It also has an arrangement with the Green Party to abstain on confidence and supply votes.
But Mr Key said on Friday 24 October voters have to consider whether they would want a government made up of Labour, the Greens, the Maori Party, the Progressives and United Future.
He says that with the country set to face difficult economic times over the next 12 to 18 months, people may not want a complicated governing structure.
"Do New Zealanders want to have what could at best be described as a five-headed monster, with seven potential leaders, all trying to get round the table and thrash out economic policy for a country that would be in the middle of a recession?"
Mr Key said a National-led government has the potential to govern alone, or with just one partner.
Key rattled, says Clark
Miss Clark, in comments made before Mr Dunne's announcement, says Mr Key is getting rattled as he knows that voters do not want any arrangement with National that brings Sir Roger Douglas into Government.
Sir Roger, a former finance minister in the 1984 Labour Government, is third on the ACT Party list.
Miss Clark says the National leader was trying to "stitch up" a Government involving ACT, United Future and the Maori Party.