Image caption The A5 dual carriageway scheme would link Dublin to the north west of Northern Ireland

A Stormont department is no longer defending a legal challenge to NI's biggest roads project.

A lawyer for the Infrastructure Department asked a judge to quash its decision to proceed with the A5 scheme.

The concession is based on approval for the multi-million pound dual carriageway upgrade having been given in the absence of a minister.

The lawyer said: "The department considers it no longer in the public interest to defend these proceedings."

Lawyers representing a campaign group behind the legal action were given time to consult with their clients before a final order is made.

Adjourning the hearing, the judge suggested it was inconceivable they could secure any better outcome.

"This is as good as it can possibly get," he said.

The roads project linking Counties Londonderry and Tyrone has been hit by delays due to court challenges.

Image caption The planned A5 upgrade runs between Newbuildings and Aughnacloy

It would involve a new 85km trunk road running from New Buildings, via Strabane, Newtownstewart, Omagh and Ballygawley, and terminating near the border at Aughnacloy.

Construction on phase one was due to begin earlier this year at a cost of £150m.

But that was put on hold after fresh judicial review proceedings were launched by umbrella group the Alternative A5 Alliance.

In 2013, the group, made up of landowners, farmers and supporters, won its first legal action against the project.

At that stage a judge quashed the decision to press ahead with the scheme, which forms part of a proposed key cross-border business route linking Dublin and the north west, due to a breach of a habitats directive.

A divisive issue

By Conor Macauley, BBC NI Agriculture & Environment Correspondent

Supporters of the road say it will bring economic and safety improvements.

Opponents have opposed the compulsory purchase of land and raised environmental issues.

They would like the existing road to be upgraded instead.

The government recently gave civil servants new powers to take decisions in the absence of ministers.

But that did not cover cases before the courts.

Crucially the bill says civil servants can retake decisions which have been the subject of legal challenge.

That means this is unlikely to be the end of A5.

In November last year, the department announced its decision to proceed with the planned route - prompting the renewed challenge.

Lawyers for the alliance were set to contest the legality of the decision being taken by the department's permanent secretary in the absence of a minister.

Their position was strengthened by a landmark ruling earlier this year in a case over a planned incinerator near Belfast.

The Court of Appeal held that a senior civil servant did not have the legal power to take such decisions without a Minister being in post.

Even though new legislation has been brought in to give greater clarity, issues still surround existing challenges.

A solicitor for the group behind the challenge requested time to consult with them

Adjourning the case until Friday, Mr Justice McCloskey noted: "It's beyond the court's conception that the applicant could find any sustainable objection to the course being proposed."