Stormont’s infrastructure minister is to appeal a judgement that ruled construction of the new A5 dual carriageway should not go ahead in its current form.

The 58-mile (94km) £1.7bn project was given the green light by Stormont ministers in October last year.

In June, a court found the Department for Infrastructure’s plans for the road did not comply with climate change targets.

The road is the Northern Ireland part of the major arterial route that connects the north-west of the island – Donegal and Londonderry – to Dublin, via towns including Strabane, Omagh and Aughnacloy.

On Monday, Liz Kimmins said she had taken the decision to instruct legal counsel to seek the appeal ahead of the deadline for doing so this Friday.

She said staff had been “working night and day” to ensure the appeal was robust.

Kimmins had said on 1 July that she was looking at “pursuing” an appeal into the ruling.

More than 50 people have died on the A5 since 2006 and campaigners have called for the road to be upgraded.

Speaking on Monday, Kimmins said she did not want to get into the detail of the grounds for her appeal until it was “formally lodged”.

She also said she advised executive ministers of her plans to appeal the judgement at its last meeting, but that the decision to take another legal challenge was hers.

She said officials in her department had been working with staff in the Department for Agriculture, Environment and Rural Affairs (DAERA), which holds responsibility for climate change targets contained in the Climate Change Act.

“It’s important we do appeal the judgement, in relation to the ruling a huge amount of work went into it, we were confident going into the case we had done as much as possible but it wasn’t to be.

“From the next day we were back to the drawing board, back working at this, and I will not be found wanting in terms of the work that will go into this to get things done.”

The minister added that she was “fighting tooth and nail” to ensure the road is built as quickly as possible.

Responding to the announcement, Benny Hurl from the A5 Enough is Enough group, which has campaigned for the new road to be built, said they fully supported the minister’s decision to appeal the judgement.

They said they were “optimistic” that the department would ensure every base was covered this time around and that would lead to a successful outcome.

Stormont’s official opposition, the Social Democratic and Labour Party (SDLP), said it was “deeply regrettable” that the decision had been taken at the “last minute”.

West Tyrone assembly member (MLA) Daniel McCrossan said: “From the hour the judgement was issued I have been urging the minister to lodge an appeal and address the court’s concerns, and there is a real sense of anger and frustration in this area that there has been relative silence since.

“The judgement was clear that there were outstanding concerns around climate targets that must be addressed.

“I cannot understand how despite several meetings with DAERA, the Department for Infrastructure and the previous Minister still failed to adequately address this. There can be no repeat of this incompetence during this appeal process.”

Deborah Erskine, DUP MLA for Fermanagh and South Tyrone and Chair of the Assembly Infrastructure Committee, said Kimmins’ decision to appeal is a “valid legal route to take, but one that will inevitably take time”.

“The Infrastructure Minister must level with people. The reality is that work on the A5 is not going to commence any time soon,” Erskine said.

“These legal processes are lengthy, and the Minister should also be looking urgently at what other steps can be taken now to make the A5 safer for all road users, and how to deal fairly with landowners impacted by the failures of DfI.”

The judicial review proceedings that culminated in Judge McAlinden’s decision on 23 June, involved a group of residents, landowners and farmers who mounted a fresh challenge against the decision to begin construction work.

The umbrella group, known as the Alternative A5 Alliance, contended it would breach legislative targets to achieve net-zero greenhouse gas emissions by 2050.

The High Court judgement blocking the upgrade of the A5 road – because the plans did not comply with government climate change targets – shows the reach and impact of Stormont’s climate change legislation – but the judgement is clear that shortcomings in the project can be remedied.

A solicitor for the Alternative A5 Alliance campaign group, which brought the successful case, said his clients’ efforts had been “vindicated” and it was an important day for the environment.

Safety campaigners from the Enough is Enough group said they were disappointed with the decision but added the judgement provided a “roadmap” for how the upgrade could proceed.

First Minister Michelle O’Neill said there was a meeting with members of Enough is Enough 1 July.

The road is the Northern Ireland part of the major arterial route that connects the north-west of the island – Donegal and Londonderry – to Dublin, via towns including Strabane, Omagh and Aughnacloy.

The dual carriageway scheme was first announced back in 2007, but has been beset by a number of delays.