TV3 has cancelled a debate between leaders of political parties in Parliament after Helen Clark and John Key refused to share the platform with minor party leaders.
A TV3 spokesman told NZPA the separate head-to-head debate between Miss Clark and Mr Key was now "under active consideration".
In a statement TV3 said the National and Labour leaders' position made broadcasting the 90-minute debate inviable and it would not be going ahead.
It had been scheduled for October 9.
Minor parties have reacted angrily.
Green Party co-leader Jeanette Fitzsimons said TV3 had been bullied by Labour and National who had colluded. The MMP parties had been gagged, she said.
"It just shows how similar the two old parties are, in their fear of diversity of views and of consultation and sharing of power that MMP demands. Anyone who can't work with other parties is not fit to lead the government of New Zealand."
United Future leader Peter Dunne accused the large parties of a backroom jackup and said TV3 was craven to buckle.
"The Prime Minister says this election is about trust -- well, we can now see that the big parties can only be trusted to look after their own narrow interests and not the interests of the nation."
ACT leader Rodney Hide made similar criticisms but said Miss Clark's motivation was that she could beat Mr Key.
"She doesn't want to have to debate anyone else or to appear onstage with (New Zealand First leader) Winston Peters."
TVNZ is holding two head to head debates between Miss Clark and Mr Key and a separate debate for minor party leaders.
Mr Key said voters wanted to be able to compare the differences between himself and Miss Clark.
"A head-to-head gives New Zealanders the most clarity to see our different styles," he said on Newstalk ZB.
Miss Clark said the issue was discussed between the two parties at chief of staff level.
"The general view was that the most benefit for the viewing public comes from head-to-head debates -- people have a very clear choice, a Labour-led government or a right-wing government. Those issues are going to come out."
In 2005 there was a row when TV3 tried to exclude Mr Dunne and Progressive Party leader Jim Anderton from a debate.
The network said eight leaders was too many, but Mr Dunne and Mr Anderton went to court and TV3 had to let them take part.