National says it will spend $267 million over the next three years on the Auckland and Wellington rail networks.

Photo: RNZ / Tom Furley

The package - just announced - includes the electrification of the Papakura to Pukekohe line, adding a third main line from Wiri to Westfield, and double-tracking the commuter line between Trentham and Upper Hutt.

The Transport Minister, Simon Bridges, said commuter rail had experienced strong growth in both regions.

He said electrification of the Papakura-Pukekohe line was a key element of the government's focus on supporting a cohesive, efficient transport system for Auckland.

He said the new Wiri-Westfield line would be dedicated to freight, thus improving commuter service on the existing lines.

Mr Bridges said while parts of the package were foreshadowed last week, more was being done.

"All of the Wellington rail work, $37 million is new, but we're making quite clear though we are funding this, we're making clear where that money's coming from and giving certainty to the region."

A total of $37 million will be spent on improving the Wellington commuter train network.

Labour Party leader Jacinda Ardern unveiled her party's plan to tackle Auckland's transport woes earlier today with her party pledging to build light rail from downtown Auckland to the airport within a decade if it wins the September general election.