The Minister for Transport, Mr Brennan, has been urged to stop Irish Rail removing a section of track linking railway lines to Galway and Mayo.
Irish Rail has said the crossover at Athenry, which links the Claremorris line with the Athenry-Limerick line, would be removed "in coming days".
Father Tony King, the parish priest of Athenry, said the move was "absolutely appalling" and he called on the Minister to intervene.
He said he understood substantial progress had been made on a project aimed at opening up a western rail corridor linking Sligo and Waterford but the removal of the crossover would be like "the nail in the coffin" for the project.
"To disrupt the prospect of this western link at a time when roads are jammed with traffic beggars belief. It is certainly causing a lot of upset and anger here," he said.
Irish Rail's spokesman, Mr Barry Kenny, insisted the removal would go ahead, stressing it had to be done for safety reasons.
He said the work was part of the mini-CTC signalling project, to modernise signalling on the Galway, Sligo, Tralee and Waterford routes.
The crossover had not been used for five years and there was no point in signalling it, at a cost of up to €750,000. Neither could it be left in place. "You can't have a few yards of track within the network without signalling. It's not desirable from an operational or safety point of view," he said.
He added that the work would not prevent services from operating in the future on the western rail corridor, pointing out that the crossover could easily be reinstated if it were needed in future.
Furthermore, Mr Kenny said, none of the track between Athenry and Claremorris was being removed and the line would continue to be maintained.