Auckland's Mayor is questioning the Northland Corridor's multibillion-dollar price tag

The 100 kilometre corridor, also known as the Northland Expressway, is made up of three Roads of National Significance, with work due to start in late 2026 on the first part, from Warkworth to Te Hana.

It's expected to cost up to 18 billion dollars.

Mayor Wayne Brown says it's ridiculously expensive and a cheaper alternative is needed sooner.

But Transport Minister Chris Bishop says it's a long-term project with national benefits, and NZTA has committed to driving costs down.