A potential legal challenge to the long awaited A5 upgrade has been described as “a crushing blow” for campaigners who have been left “appalled” by the latest obstacle to complete the flagship project.

The Department for Infrastructure (DfI) received pre-action correspondence on Wednesday which relates to a potential legal challenge to plans to proceed with construction work early in 2025.

DfI Minister John O’Dowd said he was “extremely disappointed” by the move which comes just weeks after the Executive approved the £1.2bn upgrade which includes a full dual carriageway. The Irish government has agreed to contribute £500m.

The A5 Enough Is Enough campaign group also expressed disappointment that its pleas to end opposition to the upgrade of a road that has caused almost 60 deaths since the A5 Western Transport Corridor project was first announced back in 2007 had “fallen on deaf ears”.

Chairman Niall McKenna said he is appalled by the potential legal action regarding the notorious route which has “a cruel legacy of death and destruction” that has torn families and communities apart.

“At the PAC Public Inquiry in Omagh last summer, the people of this area made their feelings absolutely clear; the new road must be delivered immediately,” he said.

“Too many lives have been lost and too many families have suffered. Despite the vast majority of people making their voices clearly heard on the issue and despite the continuous deaths, there are those who continue to ignore the realities of this life-or-death situation.

“Our pleas to reflect and reconsider have sadly fallen on deaf ears so far. It is unacceptable that a small number of people look for technical points to bring legal challenges to a scheme that is supported by the overwhelming majority of the public.

“The clear majority of people, the experts and all the main political parties have spoken in support of this scheme.

“Human life is sacrosanct and to any person who places their personal or financial needs first, we hope they will reflect upon the continued hurt that they are causing to the families of the deceased and to those who wish to protect their children in the future.”

Stormont’s infrastructure minister said he was “extremely disappointed” and warned the action could “have huge consequences for the public purse and for road safety”.

“Any further delay on this project not only has cost implications for taxpayers but, more importantly, every day that goes by risks another family receiving devastating news about a loved one that will shatter their lives,” he continued.

SDLP MLA Daniel McCrossan said the development has angered all of those involved in the “long hard slog” to progress the A5.

“Along the way there have been many obstacles but people in this area genuinely believed that finally, the end was in sight,” he said.

“News of a potential legal challenge this evening has come as a crushing blow, people are upset, angry and wondering how this can be possible.

“There has been a devastating loss of life on this road in recent years.

“I have met with families and seen first-hand the pain that they have experienced following the loss of a loved one, while others live in constant worry knowing friends and family are travelling along this road.

“It is a testament to the strength and courage of victims’ families that they have been at the forefront of the campaign to see the A5 delivered.”

The West Tyrone representative made a direct appeal to anyone considering mounting a legal challenge.

“I ask you to think of those families, of all the people who have lost their lives on this road,” he said.

“We are so close to seeing work begin on the A5 and people can’t take more years of delay and frustration.

“Do the right thing, drop this legal challenge and let this life-saving work begin.”