A fresh legal challenge has been mounted against the planned upgrade to the A5 road between Londonderry and County Monaghan.
Work was due to get under way on the road within weeks.
When complete, the new A5 dual carriageway will run for 85km (53 miles), between Newbuildings outside Londonderry and Aughnacloy in Tyrone.
The Irish government has agreed to contribute £75m over a three-year period to the project.The planned A5 upgrade runs between Newbuildings and Aughnacloy
SDLP West Tyrone MLA Daniel McCrossan accused those behind the challenge of “dragging people back into the past” and said that the new road “has the potential to both transform and to save lives”.
“It will bring necessary investment and increase connectivity which creates more jobs for people,” he said.
“It will also save the lives of the many people, especially young people, as the current road is one of the most dangerous in Ireland.”
Foyle Sinn Féin MP Elisha McCallion said the move was “merely a delaying tactic” and that she was sure the challenge would be unsuccessful.
“This latest challenge is disappointing but not unexpected given that a small group of opponents to this vital road development remain determined to delay progress against the wishes of the vast majority in the North West,” she said.
“However, having met the Department of Infrastructure recently, I am assured that the development process has been meticulously followed and have every confidence that this legal challenge will be unsuccessful.