In tandem with the lower maintenance budget, Mr Horan said a decision by Kiwirail to significantly reduce spending on wooden bridges would make cases such as the Collins Lane bridge more widespread.
Kiwirail chief executive Jim Quinn said he was more inclined to listen to the professional opinion of his staff than that of Mr Horan, who was not a railway expert.
"I have a team of people who are expert in wooden bridges, who inspect the bridges all the time and make these judgment calls from a perspective of expertise and my view is I'll back them all the time.
"Brendan keeps throwing up his deep concern for safety and saying everything's wrong with the network.
"My frank belief is that if he was that concerned about safety, he would have picked up the phone and called me."
Mr Quinn said the safety of the rail network would not be negatively impacted by the disestablishment of the track maintenance workers and the budget for maintenance, which would take a 40 per cent cut by 2014, was predicted to return to 2012 levels by 2018.
Kiwirail also responded to claims by Mr Horan that the national railway infrastructure was "rotting from the ground up". He cited a leaked document which showed Kiwirail was not responding appropriately to rotten sleepers imported from Peru.
Instead of replacing the rotten sleepers with solid hardwood sleepers, Kiwirail was replacing the rotten sleepers with Peruvian sleepers that looked "visually sound".
"That sounds like a recipe for disaster," he said.
A Kiwirail spokesperson said wooden sleepers were required to be compliant with the Australian standard, which specified they must last for at least 15 years, but some were showing decay much sooner.
"The dispute between us and the supplier is the subject of court action. In the meantime, we have put in place extra inspections to monitor decay rates and are undertaking replacement as required."