A report released yesterday shows the transport company is facing a funding gap of €103m per year
Irish Rail says it is not ordering the State to give it money.
A new report into the rail network published yesterday revealed that it needs around €500m to keep it going over the next five years.
At present, it is losing around €103m each year.
The Limerick to Ballybrophy route is one of the lines proving particularly costly, as it is costing the State €550 per passenger, per journey.
The report warns that this deterioration will see increased journey times and decreased service reliability - including service cancellations and an erosion of customer confidence.
Barry Kenny is Corporate Communications Manager at Iarnród Éireann, and he spoke to Jonathan Healy on today's Pat Kenny Show.
Mr Kenny explained: "We're not saying - and the report isn't saying - 'come along and give us the money'. It is saying 'here are the options'.
"If the view of the wider public and political powers [...] is that 'the amount of money you have right now is all you're getting', then to deliver an effective service a lot of lines have to be closed."
He also argued: "Ultimately you've got to work within the resources you have. And if you have limited resources - as we have had for a number of years - are you going to put money into the route where three million people are travelling - [like] Dublin-Cork - or the route where 23,000 people are travelling?
"People who live in these communities will have very strong views. People who don't live in these communities will have very strong views. The public consultation launched by the National Transport Authority will allow everyone to have their say before decisions are made in the future - because, as I say, one way or the other there is a difficult decision ahead," he added.
Dr Sean Barrett, Transport Economist at Trinity College, told Newstalk Breakfast some of the routes losing money may not be sustainable.
"I think the case for them is very weak - like Ballybrophy, like Limerick-Waterford," he suggested.
"Railways need built-up areas, and ones that take an hour longer than a railway line running parallel to it don't really make much sense."