KiwiRail bosses say thousands of rotting wooden sleepers spread along its rail network do not pose a significant risk to the public, despite fears they could trigger a derailment.
The state-owned enterprise has come under increasing scrutiny of late after announcing plans to chop 181 staff.
The redundancies include 50 staff in the company's northern region, which encompasses the Waikato.
KiwiRail, which employs 4100 staff nationwide, also confirmed rail inspections revealed about 7000 of its imported wooden sleepers were defective and needed replacing.
About 55 decaying sleepers have been identified in the Waikato.
KiwiRail chief executive Jim Quinn said inspections of about 100,000 imported sleepers from one supplier found about 7000 were showing signs of premature decay.
Extra inspections had been set up to monitor decay rates and the company aimed to replace all defective sleepers by early next year, he said.
But New Zealand First MP Brendan Horan said Mr Quinn's assurances were "laughable" in light of the announced job cuts.
"So much of what KiwiRail is saying doesn't make sense and the fact that they're getting rid of maintenance staff is insane," Mr Horan told the Waikato Times.
"KiwiRail are saying they know where the rotten sleepers are but I understand they don't.
"Some of these sleepers could be located at our many road crossings. If those sleepers happened to collapse, it could trigger a derailment and that would be catastrophic, especially if it happened in peak hour."
Mr Quinn said KiwiRail had already replaced sleepers with advanced decay and had prioritised further replacement work based on testing and inspection.
"We have a replacement programme for the rest under way to ensure the safety of staff and commuters; we simply would not run services if we suspected the network was not safe."
Mr Quinn said KiwiRail would spend $750 million on its rail network over the next three years - about $200m less than planned before the economic downturn.
"However, it is important to note that our revised planned spend is still around four times more than we spent in 2005, which means we are still making a significant investment."
But Mr Horan said the defective imported sleepers were another example of a "cheap deal" that had backfired on KiwiRail.
"We also have reports that KiwiRail's new locomotives from China are breaking down and damaging the tracks.
"What the Government needs to do is invest more into KiwiRail and its staff.
"We need to invest in infrastructure to make sure it's efficient."
- Waikato Times
What do you think of the new banknotes?Related story: Better, brighter Kiwi banknotes