National leader Don Brash has quashed any suggestion that his party could form a coalition government headed by New Zealand First leader Winston Peters.
But the Prime Minister said she was sure both leaders were "desperate and dateless" enough to consider such a scenario.
Their comments follow a report inyesterday's Herald which said MPs in both National and NZ First were informally discussing a power-sharing scenario in which Mr Peters would be Prime Minister - for half, if not all of, a three-year term.
The outcome would be possible only if NZ First held the balance of power after the election.
NZ First negotiators suggested such a power-sharing deal between Mr Peters and National PM Jim Bolger during coalition talks in 1996.
Helen Clark said yesterday that the same proposal was raised with Labour during talks that year.
Mr Peters yesterday said he knew of no MP within his caucus who held the power-sharing view "let alone one silly enough to discuss it with anyone".
He dismissed the Herald report as a "silly orchestrated rumour started by disaffected members of the National Party".
National insiders suggested the rumour had been sparked by overly optimistic NZ First MPs or the Government.
Dr Brash initially refused to speculate on coalition outcomes, simply describing the power-sharing scenario as "wild talk".
But yesterday he went further and ruled it out.
"This is an attempt by a small party to try to squeeze in, and we're not having a bar of it ... We will not sell our souls just to get into office and we most certainly will not be offering the leadership of the next government as a bargaining chip."
Helen Clark said of the power-sharing possibility: "I'm sure they're desperate and dateless enough to consider it, both of them.
"I can assure you the same sort of thought was around in 1996 and got short shrift then."
National voters would respond to the idea "with horror".
Asked if she would ever consider such a power-sharing deal with Mr Peters, she laughed: "There's 101 reasons why it would not be considered."
But she did not rule out other negotiations with Mr Peters post-election.
