The National Party has promised to create a $500 million Pothole Repair Fund for repairs to local roads and state highways if its elected.
The Green Party has criticised the plan, saying the work is already being done.
But National's transport spokesperson Simeon Brown told Morning Report the roads are the worst they have ever been, and are unsafe to drive on.
Asked whether this was a political gimmick Brown said: "Not at all, this is a reality of our roads being in the worst state they've ever been and the need for us to be investing in making sure that they are safe to drive on so we can keep our economy moving."
Roads were critically important to a productive economy, he said.
The government was spending $2.8 billion on highway maintenance, saying it was a 65 percent increase on what the previous National government had spent.
Brown said the government was spending more but delivering less for roading renewals.
"What we're saying is we want to double that current rate and get it back to a sustainable level of investment and this is what this fund will be directed towards so that our roads ... aren't falling apart."
The money for National's policy would come from money put aside for speed reduction.
"What we're saying is actually the Road to Zero fund, which has got a billion dollars being allocated to it each year, it has significant delivery challenges. Within it they promised 300 kilometres of median barrier by 2024, they've only delivered 50km so far.
"We're going to take a portion of that money and we're going to reallocate that to making sure our roads are actually safe to drive on."
National would not continue with blanket speed limit changes, he said.
Asked if the evidence shows cutting the speed limit would significantly reduce the road toll and save lives, would it not be worth pursuing, Brown said National wants to improve the quality of the roads - also a contributing factor, he said.
"We need to get the balance right between safety and efficiency."
Transport Minister David Parker told Morning Report in 2018, the government repaired 39,000 potholes and in 2022 it repaired 54,000.
"The maintenance budget's gone up from $1.7b over three years when they (National) left office to $2.8b under us - a 65 percent increase.
"You've got to ask yourself, with those increases, what's the underlying problem and the underlying problem is actually very simple for people to understand - the last government stopped resurfacing roads - or they froze the funding for maintenance - and therefore the number of roads that could be resurfaced."
If roads were not resurfaced, water would get in and cause potholes, Parker said.
The government was resurfacing more roads than necessary just to maintain things, he said.
The weather this year was also to blame in areas, he said.
Brown had earlier told Morning Report there had been a 27 percent reduction in relaying of roads under Labour.
Parker said that was "absolutely wrong".
"Actually he knows that, that is so, with respect, dishonest because he was at a select committee where I showed him the graph of the kilometres of road that have been resurfaced now compared with the halving of it when he was in government, or when his party was in government, and they froze the maintenance fund."
On the issue of median barriers, Parker said the government had done "hundreds of kilometres of median barriers".
Parker said he also thought less could be spent on speed bumps to instead be put into pothole repairs.
"I believe that potholes are a safety issue and that that justifies the reallocation of some money within the safety budget but you can't get $500m out of the safety budget and not have a decrease in road safety."