Labour is denying it made a deal with the Greens in Ohariu and says electoral law should be changed to prevent the sort of "rort" that National and ACT have stitched up in Epsom.
The Green's Ohariu candidate in the November 26 general election, Gareth Hughes, has said he will campaign for the party vote only.
That should help Labour's Charles Chauvel in his bid to win the seat.
He came close to defeating United Future leader Peter Dunne in 2008, and would have if Green Party supporters had given him their electorate vote.
In Epsom, National is going to campaign for the party vote so ACT candidate John Banks can win the seat.
ACT has to win a seat to get MPs into Parliament because it is polling well below the 5 percent threshold for parties which do not win an electorate.
Mr Dunne, who has held Ohariu since 1984, has accused Labour of hypocrisy for previously criticising National's tactics.
Labour leader Phil Goff said today there was no deal with the Greens in Ohariu.
"No discussion has been entered into...it's not even an understanding," he told reporters.
"If the Greens' candidate is saying he is going for the party vote, that's his decision."
Mr Hughes said on his party's website yesterday the Greens would campaign for the party vote in Ohariu "just like in every other electorate" and there was no deal with Labour.
Mr Goff said circumstances in the two electorates were different.
"The rort in relation to Epsom is that normally an ACT candidate would not get elected there, and as a result there would be no ACT Members of Parliament," he said.
"What National is doing is setting up ACT to win that electorate and coat-tail four or five other MPs into Parliament."
Mr Goff said that defeated the purpose of the 5 percent MMP rule.
"There is a loophole there, and it should be closed...I believe the system should be changed," he said.
Mr Dunne is also getting help from National, which is going to run a party vote campaign in Ohariu.
Mr Chauvel said last week the same thing happened in 2008 when there was a three-way split, with Mr Dunne winning the seat, Labour second and National third.
Mr Dunne gained 12,303 votes, Mr Chauvel 11,297 and National's Katrina Shanks 10,009.
Mr Chauvel said he expected the same pattern this time, with the difference being that the Greens had said they would campaign for the party vote only.
"If their supporters follow that urging, then given the decreasing popularity of Peter Dunne and the increasing view that he is irrelevant, I personally think things are looking pretty good," he said.
