Mr Justice Gerry McAlinden ruled at the end of June that the Department for Infrastructure had failed to show the decision was compatible with statutory climate change targets.

He acknowledged that his decision would bring “fresh anguish” to those affected by accidents on the existing A5 road and that one of the primary justifications for the construction of the new road “is that it will be much safer than the existing road”.

However, he said the “principle of the rule of law cannot be subverted, even if the motivation for doing so is to achieve what is deemed to constitute a clear societal benefit”.

Liz Kimmins, the infrastructure minister, yesterday confirmed that her department will appeal the judgment.

“There is too much at stake for us not to appeal the recent court judgement about this regionally significant infrastructure project,” she said.

“I am prepared to do everything within my power to save lives on this stretch of road. The people of this area have suffered enough and with them in mind we are lodging this appeal.”

She added: “This project has the backing of the Executive and the Irish Government. It is a complex matter which has seen many years of hard work and collaboration to get it to this point.

“My officials have been working very hard to ensure that no stone is left unturned and that we submit a robust appeal to the court.

“I am determined that this road will be built and it is important that everyone who wants to see this happen works together in a constructive way to achieve that goal.”