The group campaigning to get rid of the MMP system says a meeting between National Party leader John Key and ACT's candidate for Epsom is a shonky manipulation of the voting system.
On Friday, Mr Key and John Banks met informally for a cup of tea in a Newmarket cafe. The meeting is viewed as a signal to National supporters that they should give their electorate vote to Mr Banks.
That will increase ACT's chances of winning Epsom and remaining in Parliament, providing National with a useful ally in any deals after the election.
But Vote for Change spokesperson Jordan Williams says for a party leader to endorse another so he can have as much power as possible after the election is fundamentally unfair and shows how flawed the Mixed Member Proportional voting system is.
Mr Williams believes people should vote for change in the referendum on MMP to stop what he calls this type of political circus.
People can vote in the referendum on election day on Saturday, 26 November. If more than half choose to keep it, the system will be reviewed.
If MMP is rejected, Parliament will decide whether to hold a further referendum in 2014 to choose between MMP and the most popular alternative system.
The other choices are: First Past the Post, Preferential Voting, Single Transferrable Vote and Supplementary Member.
The results of the referendum will be released in December this year.