Assurances taxpayers won't bear the brunt of costs from a landslide threatening the new Pūhoi-Warkworth motorway.

Cracks have appeared in concrete barriers and it's possible sections of land are moving under the one-month-old road.

Transport Minister David Parker says he's expecting a briefing, and this could potentially be a safety risk for motorists.

Waka Kotahi has acknowledged it knew the land was unstable.

General manager of transport services Brett Gliddon says the builder reported on how to fix it and they continued with the opening.

"They're responsible to fix it, so they have to maintain and operate it for 30 years. And in 30 years, they hand that back to us, the Crown."

LISTEN ABOVE

• ‘Slow-moving landslide’: Fears for Pūhoi-Warkworth motorway
• 'Potentially a safety risk': Minister to be briefed on Pūhoi-Warkworth motorway