New Zealand was ranked 39th on the most recent electoral freedom ranking – one place below Australia. Ireland topped the list and Brunei came in last place.
In response to Reti's request for comment, the Foundation's Head of Research José Antonio Peña said: "Any new rule which objectively increases the power held by the political party apparatus would most likely weaken the MPs' individual standings as representatives of his or her constituents.
"This and any distortion of the voter's will is seen as a regression by WEFI standards and will certainly reflect on the country's performance in upcoming editions."
National Leader Simon Bridges said New Zealand has always been famous for its level of freedom and transparency.
He says Peña's comments show New Zealand's WEFI ranking will take a hit as a result of the Waka jumping bill.
"Put simply, it puts the power of political parties above that of MPs to represent their views and the views of their constituents. It's a disgrace it's going to pass in this Parliament."
Little – the Minister responsible for the bill – disagrees with Bridges.
"I don't think the bill will do any damage at all to New Zealand's electoral integrity – it maintains the fundamental principles of MMP which is about party representation in Parliament.
"This Government has made a decision to have the electoral integrity legislation and that's what we're doing."