Prime Minister John Key has poured cold water on Auckland Mayor Len Brown's plans for a $2.4 billion inner-city rail loop.

Only hours after Mr Brown talked up the rail loop at yesterday's public launch of the draft Auckland Plan, Mr Key said it was not going to happen anytime soon.

Mr Brown has made building the rail loop by 2018 a core plank of his mayoralty and yesterday called it a "game changer" in the context of the Auckland Plan.

Speaking to Newstalk ZB, Mr Key said he was not convinced of the merits of the rail loop, as consultants had told the Government it would not get many people out of cars, rather it would take people out of buses into trains.


He said the council was "abundantly aware" the Government might provide some money, but was not going to pay for the whole project.

"I'm not saying it is not going to happen, it is just not going to happen in a heartbeat.

"The ratepayer of Auckland needs to know what they are on the hook for, because central Government is not going to pay for it."

Mr Key's comments are the latest shot in a series of clashes between the Government and Mr Brown over the merits of the rail loop and the second time in a month that Wellington has expressed a concern about the Auckland Plan.

Several Cabinet ministers chastised councillors over the compact city model promoted in the plan, claiming it would force land and housing prices up.

They wanted it abolished, or at least made more flexible.

Mr Key and Transport Minister Steven Joyce's concerns about the rail loop are making it difficult for Mr Brown.

Last night, Mr Brown played down Mr Key's comments as nothing new, and said his thoughts on the timeline for the rail loop had not changed.