Translink has been accused of treating Derry as 'second best' following a raft of recent disruptions on the line from Belfast to the North West city.
Rail lobby group Into the West said that they were "dismayed" that Translink continued to divert trains on the Belfast- Derry line to Portrush seemingly "whenever the mood takes them".
The anger and frustration comes after the service was terminated at Coleraine and passengers on board had to be transferred to Derry by bus.
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Its also been claimed that Northern Ireland's rail operator has been also been diverting the service to Portrush to accommodate people heading to the North Coast during the period of good weather this week.
Into the West spokesperson, Steve Bradley told MyDerry that Northern Ireland's two main cities should have a "fast, direct, frequent and reliable" rail service between them.
"That service should not be tampered with in the Summer months because people are travelling to the North Coast, and it wouldn't happen anywhere outside of NI," Mr Bradley said.
"This confirms a worrying trend within Translink's senior management in which the North-West always seems to be treated as second best. The three stations West of the Bann on the Derry-Belfast line receive a significantly lower quality and frequency of service than every station East of the Bann does on the same line.
"And most of this is down to simple timetabling decisions, not structural limitations. Translink is consciously choosing to provide a poorer service for NI's second city, and it is unacceptable.
"Derry rail station has had the fastest passenger growth on the island in recent years, but at times it can feel as if Translink want to suppress that growing demand.
"They need to stop diverting trains on the Derry-Belfast line to Portrush. And they must finally adopt the principle that every station in the west should receive the same service as every station in the East does on the same line, to bring this blatant East-West discrimination to an end".
Translink said it was committed to services in the North West and that all future services would remain "under review". A spokesperson said: “The North-West timetable is designed to offer Belfast to Derry~Londonderry through trains, with the Portrush line serving as a connecting route in Coleraine.
“When there are considerably larger numbers of passengers travelling onwards to Portrush, primarily during the summer months, a decision can be taken, on grounds of passenger safety, to reschedule the train to operate direct to Portrush.
"Passengers for Derry~Londonderry then make a direct rail connection from Coleraine to Derry. When there is other disruption/delays on the railway Translink will use all available alternative public transport services to assist passengers with completing their journey.
“Translink has invested nearly £74m on significant upgrades on the rail network and associated infrastructure to the North West in recent years, including the North West Transport Hub, offering modern, comfortable passenger facilities.
"We also invested in an hourly train service between Belfast and Derry. Options for the Phase 3 upgrade to the Coleraine to Derry railway line are currently being assessed by the Department of Infrastructure. If approved, we will be in a position to start work on this important project for the North West."
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