The company is facing a funding gap of €103m per year
Irish Rail commuters could be facing longer journey times and a decrease in service.
A new report has warned that the company is facing a funding gap of €103m per year from 2017 to 2021.
The Rail Review 2016 Report was published Tuesday.
It says an increased funding of this level per year will bring the spending on the maintenance of the network and the fleet up to an appropriate level and start the investment in refurbished and new fleet to meet future growth.
But it cautions that the current level of funding is "unsustainable" and is the primary cause for the deterioration of the infrastructure.
"The consequence for underfunding is increased safety risks and unacceptably high commercial risks to the various revenue streams, which in turn runs the risk of the company incurring further losses and entering insolvency", it adds.
It also warns that this deterioration will see increased journey times and decreased service reliability - including service cancellations and an erosion of customer confidence.
"Inevitably this will result in reputational damage leading to significant revenue loss and a decline in customer satisfaction.
"It is not inconceivable that a journey time deterioration of 10 minutes across our intercity network would occur each year due to asset failure arising from this under investment."
Such a situaion would mean an extra 50 minutes on to journey times by 2021.
The report says that providing appropriate funding levels over the next few years will bring the infrastructure to a "steady state condition" by 2030.
While it also finds that State funding required to maintain the network has increased from €247m in 2011 to €276m in 2015.
It also identified four of the poorest performing routes on the network: Limerick - Ballybrophy, Limerick Junction - Waterford, Limerick - Galway and Dublin - Rosslare.
The report also says that all five stations between Ballybrophy and Limerick, all four stations between Limerick Junction and Wateford, and three stations between Ennis and Athenry were all among the 15 least used on the network with less than 40 passenger movements.
One of the lines in question caused controversy when it emerged it has been carrying just 73 passengers a day - and costing the state €550 per person.
Speaking at the launch of the report, National Transport Authority CEO Anne Graham said: "Rail has a huge role to play as an economic driver in terms of bringing about balanced regional development.
"It also delivers social benefits by improving social inclusion, improving accessibility and mobility, and making travel safer. In addition, it provides real environmental benefits by reducing emissions and improving air quality.
"But these benefits do not come free of charge, and if safeguarding them into the future is to become a genuine priority, there must be a commitment to give our rail network the support it will need in the years ahead.
"The Rail Review looks at the investment required to operate, maintain and develop the network, identifies the funding gap that has arisen, and examines the options around closing that gap.
"Starting today, we are actively consulting with the public on the prioritisation of rail services. We are very anxious to get a wide a range of views, and we want to engage with as many people as possible in this process, including members of local communities, rail users, employers, and any other interested parties."
Written submissions and observations may be made: