Labour leader David Cunliffe confirmed he would still be open to a post-election deal with Internet Mana despite making the abolition of "coat-tailing" under MMP a priority for a Labour-led Government.
Prime Minister John Key said that makes him hypocritical; Mr Cunliffe said Mr Key was "unconstitutional" because he had rejected a recommendation by the Electoral Commission to get rid of the one-seat rule.
The one-seat rule, known as coat-tailing, exempts a party - or a formal alliance such as Internet Mana - from having to reach the 5 per cent threshold for Party Votes if it wins an electorate seat.
Mr Cunliffe said Labour would begin moves to abolish the one-seat rule and reduce the 5 per cent threshold to 4 per cent within 100 days of becoming Government. So a party with one seat but less than 4 per cent of the party vote would get only one MP whereas now it would be able to claim four or five MPs.
Asked if he would rule out dealing with Internet Mana after the election, Mr Cunliffe said the rules of this election will ultimately be fought on the basis of the rules the Government decided "and will have to consider, once the public have had their say, what we'll do". He scoffed at Mr Key describing that as hypocritical.
"This is a Prime Minister who has done craven cups of tea with the Act Party leader and who has tried to beat the drum for the Conservatives and may yet install them in a National seat so the Prime Minister is in no position to sermonise."
Mr Cunliffe called on National to support a private member's bill in the name of Iain Lees-Galloway abolishing the one-seat rule.
In 1999, Winston Peters' win in Tauranga allowed him to bring in four more New Zealand First list MPs, with the party vote at 4.26 per cent.
In that same election it was made clear to Labour voters in Coromandel, where Greens co-leader Jeanette Fitzsimons stood, it would be acceptable to vote for her in the electorate vote, in case the Greens fell below 5 per cent.
She won the seat but her electorate seat was not needed to coat-tail more Greens across the line because the party made it with 5.16 per cent, making seven MPs.