IARNRÓD Éireann has insisted that it isn't cutting back on maintenance work in the face of mounting losses after it emerged that speed restrictions have been placed on more than 25 miles of the Dublin-to-Cork railway line due to safety concerns.

The affected stretch, which runs between Newbridge and Portlaoise, is the busiest intercity line in the country and is used by all services to Cork, Galway, Limerick, Waterford and Tralee. Although most services on these routes are still arriving on time, this is because the timetables haven't been redrafted to take advantage of the new intercity trains currently being introduced.

The new 75mph speed limit, which is up to 25% slower than the previous speeds, means that passengers will not experience the full benefit of the trains, which were bought at a cost of more than €500m to the taxpayer.

A spokesman for campaign group Rail Users Ireland said it was concerned the speed restrictions reflected cutbacks in maintenance work. "Track repairs have to be done at night and the issue this raises is whether they have cut the overtime budget to cover night work," he said.

"The speed restriction seems to be permanent for the foreseeable future. They have even removed the old higher speed limit signs."

An Iarnród Éireann spokesman said the company hadn't cut its maintenance budgets and that any suggestions to the contrary were "ridiculous sensationalism". He said the speed restriction on the Cork line had been introduced due to drainage problems on the line caused by record rainfall in recent years.

"We are about to undertake a programme of maintenance and renewal in relation to this but regrettably we have no control over record rainfall."

He added the speed restrictions didn't undermine the benefits of its new intercity train fleet because they were long-term investments, which would last for another 30 years.

"Furthermore, the improved performance being delivered by the intercity rail fleet ensures that speed restrictions will not impact negatively on journey times."