The Green Party fears time is running out to make changes to the MMP voting system before the general election in 2014.
An Electoral Commission review of the Mixed Member Proportional system released in November last year recommended changes to the thresholds for parties to enter Parliament.
The recommendations include dropping the party vote threshold from 5% to 4% and scrapping the coat-tails rule.
That would stop a party that won an electorate seat bringing in extra list MPs, unless it reached the party vote threshold.
The Justice Minister approached other parties in March this year to ask for their views on the commission's recommendations.
A spokesperson for Judith Collins says all but one party has replied, but work has not begun on analysing the responses.
The Green Party's electoral reform spokesperson, Holly Walker, says consensus is unlikely and the Government should adopt the commission's recommendations as soon as possible so legislation can be put in place.
The Labour Party is disappointed with the rate of progress, but says there is still time to make changes before the election.
Associate justice spokesperson Lianne Dalziel says her party will work constructively with the Government and it supports the commission's recommendations for the threshold changes.