New Zealand First MP Brendan Horan is calling for heads to roll at KiwiRail, despite the state-owned company saying it is responding responsibly to the discovery of a batch of rotting railway sleepers.
Last week Mr Horan, who is based in Tauranga, released what he claimed was a leaked KiwiRail document detailing rotting railway sleepers infected with a Peruvian fungus.
Mr Horan said KiwiRail's policy of replacing rotten sleepers with "visually sound" sleepers was a "recipe for disaster".
KiwiRail responded by releasing a statement about how it was dealing with the sleepers.
"In order to seek further understanding about the fungus type causing the decay in some of our imported sleepers we commissioned independent DNA testing," said chief executive Jim Quinn.
"Test results just received by us on a consignment of sleepers contained at one of our workshops indicated that two of the fungus types are new to New Zealand.
"Testing confirmed that these pose no danger to humans and the Ministry of Primary Industries (MPI) is currently investigating whether the fungus poses any biosecurity risk.
"However, we are now taking extra steps as recommended by MPI to sanitise and contain the sleepers we are systematically removing from the network.
"Until we have resolved a disposal strategy with MPI we will be applying a household bleach solution to the sleepers as they are removed from the network and then keep them covered as we transport and store them."
"The results of the testing that found potentially unwanted fungus types only relate to the consignment of sleepers that are being held at our workshop.
"The initial testing we commissioned on sleepers on the network found they contained a fungus common to New Zealand."
"Despite this we are implementing a no-risk approach. Even if it turns out the sleepers we are removing don't contain the unwanted fungus type, the extra measures we are taking are a responsible move."
Mr Horan said the sleepers posed a "massive security risk right across the country".
"The damage that these two new fungi could inflict on the environment could be dramatic."
"Either KiwiRail imported untreated wooden sleepers, or the treatment process was useless."
"KiwiRail management must now do the right thing and make those responsible for this blunder pay with their jobs."