The Government is coming under pressure to adopt electoral reforms which would have diminished National's power at the last election.
Opposition parties say the Government should adopt all the Electoral Commission's recommendations for MMP reform, which were tabled in Parliament yesterday.
"The review shows that it is well and truly time to ditch the so-called 'coat-tails clause' to avoid stitch-ups like the deal done over the tea cups by John Key and John Banks last election," said Labour leader David Shearer.
"We now have an opportunity to restore that trust so Kiwis can be confident the electoral system works in the best interests of the country, not individual politicians."
The report followed an independent review after last November's referendum in which a majority of voters chose to keep MMP.
Labour MP Lianne Dalziel said the thresholds must be implemented in time for the 2014 election.
"The Electoral Commission says these changes don't require a referendum, which means we need to just get on with it. The integrity of the 2014 election requires these changes be made," Ms Dalziel said.
The Green Party also backed the recommended changes, which it said reflected the underlying principles of fairness, proportionality and diversity in the electoral system.
"It's vital that the National Government does not allow the immediate political interests of any single party to get in the way of changes that strengthen our electoral system in the long term," Green Party electoral reform spokeswoman Holly Walker said.
"This isn't about the next election; it's about the next 10 elections."
In its final report the commission recommended several changes to the MMP system, including lowering the party threshold to 4 per cent from 5 per cent and abolishing the one electorate seat threshold.
National would have lost a seat and would have been forced to depend on the Maori Party for a majority on confidence votes had last year's election been fought according to the Electoral Commission's final recommendations on the future of MMP.
With Parliament fixed at a maximum 120 seats, National would have held 58 seats rather than 59. All other parties would have retained their current entitlements.
The two seats Act and United Future won between them would not have been enough to secure 61 seats and a governing majority without the additional help of the Maori Party's three seats.
Act leader John Banks criticised the report and said his party would not support the proposed changes.
"Voting systems benefit from infrequent change," he said.
"Voters will not have any confidence in the electoral system if it can be continually tinkered with."
Justice Minister Judith Collins said almost 6000 submissions were received during the review, including more than 1000 on changes proposed in August.
Lowering the party threshold to 4 per cent.
Abolishing the one electorate seat threshold.
Abolishing the provision for overhang seats.
Parliament consider fixing the percentage ratio of electorate to list seats at 60:40.