A “slow-moving landslide” is threatening the new Pūhoi-Warkworth motorway barely a month after it opened to traffic, RNZ reports.

Cracks have appeared in concrete barriers on the motorway and the slope above one section is shifting up to 30cm a week at times, according to Waka Kotahi reports provided to RNZ. The landslide was set off by the Auckland floods early this year.

There were also rockfalls at four other places in the area. Waka Kotahi is now carrying out emergency stabilisation works.

RNZ reported the agency had known for years that the land in the area was unstable but had thought the motorway would bypass it.

The new motorway opened to motorists on June 19.

The 18.5km Ara Tūhono motorway from Pūhoi to Warkworth motorway opened to traffic on June 19. It shaves an average 11 minutes off the drive north for about 35,000 vehicles a day and provides motorists with a smoother and safer journey to the dangerous section of SH1 it replaced.

Over the years, the project has been opposed and mocked by Labour as a low-value “holiday highway” and was started by the last National government as part of its “Roads of National Significance” programme.

When opening the motorway, Prime Minister Chris Hipkins said it was not wrong to criticise all of the road funding going into the Roads of National Significance and away from maintenance and local roads.

“The reality is we need to do both. We need to invest in new roads but also make sure we are maintaining the existing roads,” he said.

Asked if National should be opening the motorway when they started it and Labour criticised it, Hipkins said “and we funded it”.

“There are lots of people who will want to claim credit for this but the fundamental, big important question is let’s get these projects moving.”

The new 1.35km Matakana Link Rd opened at the same time as the new motorway. Photo / Auckland Transport

The Prime Minister said the new motorway is the most significant new road since Transmission Gully, which has transformed travel in and out of Wellington where he’s the MP for Rimutaka.

National’s transport spokesman Simeon Brown accused Labour ministers of “shamelessly” celebrating the completion of a project started by National after calling it a discredited “holiday highway”.

He welcomed the opening, saying it is a big win for the Auckland and Northland region and pleased to see it open after years of delays.

The motorway, which took nearly seven years to build, was initially due to open in the summer of 2021/22 and then at Queen’s Birthday weekend last year, but the impact of Covid pushed out the opening date by a further 12 months.

Waka Kotahi general manager transport services Brett Gliddon said the motorway has been built to the highest safety standards and strengthens the resilience of the roading network between Auckland and Northland.

Auckland Transport chief executive Dean Kimpton said the 1.35km Matakana Link Rd, just south of the new roundabout at the end of the new motorway at the Warkworth end, will bring transformational changes to Rodney.