In Focus - Prime Minister John Key tells Morning Report Labour's announcement on Auckland light rail is "panicky" and all about the Mt Roskill by-election.
Labour is proposed splitting with Auckland Council the estimated $1.36 billion price tag of a light rail service from Mt Roskill to the city centre but mayor Phil Goff is questioning whether the council should have to pay for it.
Mr Key told RNZ's Guyon Espiner that light rail was notorious for cost blowouts so the price tag would be much more.
"Auckland Council, Auckland Transport and the New Zealand Transport Agency have been working together on the 20 year plan - they have light rail theoretically in the 2028 proposals, around that sort of time.
"One of the things that's yet to be determined, as I understand it, is whether rapid bus would be much better.
"The second thing with light rail is it's notorious for blowing out in costs."
In Australia a rollout of light rail was billions of dollars over budget, he said.
"I think you've really got to do that proper work on whether rapid bus might be better than light rail.
"You wouldn't want to race out there with what is a $1.4 billion promise but in reality will be more than that.
"That's quite an expensive promise to win a by-election for a seat they've held for a very long period of time when ... other new Zealanders and other Aucklanders are going to have to pay for that."
The government was investing in solutions for Auckland transport including the the Waterview Connection which would open up a new route, he said.