Traffic backed up after a crash on State Highway 1 on the Rakaia River bridge last month.

A Canterbury MP has launched a petition to four-lane State Highway 1 from Christchurch to Ashburton.

Andrew Falloon, the National MP for Rangitata, wants the Government to push ahead with the previous Government's promise to upgrade the "dangerous" 80 kilometre stretch of road.

Last year the then National-led Government pledged to widen the road to four lanes as part of a $10.5 billion nationwide roading upgrade. The plan was not approved by Cabinet or put through New Zealand Transport Agency's budget process.

MYTCHALL BRANSGROVE/STUFF Rangitata MP Andrew Falloon says the existing highway from Christchurch to Ashburton is congested and dangerous.

"Recently in Parliament I asked the Transport Minister [Phil Twyford] to commit to building the road. He refused to do so," Falloon said.

"I think that's wrong, and I think most Cantabrians think so too.

"The existing road is becoming a handbrake on Canterbury's growth and Labour has cast doubt over the continuation of the planned project to extend the highway."

ALDEN WILLIAMS/STUFF Road cones on SH1 near Rolleston.

He described the stretch of highway as congested and dangerous.

On average several road users a year lose their lives on the stretch of highway. The road includes New Zealand's longest road bridge, the 1.75km-long Rakaia bridge.

At present Christchurch's southern motorway project includes four-laning the highway to just north of Rolleston.

CHRIS MCKEEN/STUFF Judith Collins is the National Party spokesperson for transport. She says the Government's "obsession with light rail" in Auckland threatens regional roading projects.

Falloon's petition is part of a campaign by several National MPs to push regional highway safety projects. They will present the petitions to the Government later in the year.

National's transport spokesperson, Judith Collins, said the Government was reviewing roading projects from to Northland to Ashburton as it tried to divert billions of dollars to "pet light rail projects" in Auckland.

Collins said the "Government's obsession with Auckland trams" placed a number of regional highway projects at risk.

ANDREW GORRIE/STUFF National wants the Government to confirm its support for major roading projects.

A spokeswoman for Transport Minister Phil Twyford said the concerns were ill-founded and the petitions were stunts to protect campaign promises, rather than actual roading projects.

"The Transport Agency has advised that funding for road upgrades cannot be redirected into rail, so National's concerns are unfounded.

He acknowledged the Government cancelled upgrading Auckland's east-west link, but said other "highway projects" referred to in National's petition were election campaign promises made by National and never costed or funded.

STUFF Regional highways can be hotspots for crashes and fatalities.

"To suggest the Government isn't going ahead with projects that don't exist is misleading. And to suggest non-existing funding be diverted into rail is nonsensical."

The call has come just after the holiday period in which 12 people died across the country. Last year, 380 died on New Zealand roads – the highest toll since 2009 when 384 people died.

Collins said the projects were all prioritised to improve safety and travel times, better connect the regions and boost regional economic growth.

Falloon said demand on State Highway 1 south of Christchurch would only increase because of activity at Timaru's PrimePort and the inland port at Rolleston.

International tourist numbers more than doubled in 15 years and there were more trucks on the road, he said.

"We need to be investing in the critical infrastructure that supports growth in our regional economies, not putting all our eggs in one basket with Auckland."

* Comments on this article have been closed.