Electorate reform likely spells bad news for Labour

The battlelines have been drawn for the next election and they could change the shape of Parliament.

Our electorate boundaries have had to be redrawn after the release of census data - but the proposed changes in South Island may make things more difficult for Labour.

Flat Bush in south-east Auckland is likely New Zealand's newest electorate - it's diverse, with a mix of state homes, first homes and established beachside properties.

The new electorate will be created by carving off parts of the current Papakura, Hunua and Manurewa electorates, where there's been huge population growth.

Newshub has crunched the numbers and if people vote like they did at the last election, a National candidate would likely win the new seat.

The bad news for Labour doesn't end there. Changes to two South Island seats means they're no longer sure bets for Labour.

Port Hills has been renamed Banks Peninsula and picks up part of the safe National seat of Selwyn and Dunedin South gets voters from Clutha-Southland - another blue seat.

National leader Simon Bridges likes the new-look South Island.

"I mentioned the West Coast, you've mentioned Port Hills, there's seats like Flat Bush," he says. "Even Dunedin South is a seat we'll be working for."

Prime Minister Jacinda Ardern says she thinks the system is a "good one".

There are small changes to the seven Māori electorates; Tamaki Makaurau picking up Te Atatu south and east Manurewa.

However, Māori electorates are larger than general electorates by about 2000 people and span the largest regions.

"It's hard, there's no doubt about it and it's tougher all the time," Labour MP Willie Jackson says. 

"It's a shame we don't have more Māori electorates but that's just how it is."

The proposed new boundaries are open for feedback for the next month.