Video: A5 road cost soars above £1billion, Derry section could start in 2020 but further challenges expected, Infrastructure Committee told

Ms. Mallon said she was hopeful of work starting this year pending a public inquiry in a fortnight. She issued the confirmation after John McGrath, deputy secretary of transport and resources at DfI, updated the Stormont Infrastructure Committee on the huge costs.

He said the A5 and A6 were among infrastructure commitments in the ‘New Decade, New Approach’ accord that would involve massive departmental expenditure.

“If it has to be funded by the taxpayer, you are talking about large sums of money. The document talks about the A5 and the A6. The A5 alone would be about £1 billion, and there would be further funding for the A6 before you get to water [funding for water infrastructure]. These are big numbers.

“If it remains the case that they have to be funded from taxpayers’ money, the situation is that the numbers are bigger, almost, than the current NI block. It is not just a matter of will; it is a matter of securing the funding,” he said.

Dr. Andrew Murray, DfI’s deputy secretary of roads and rivers, said work on Newbuildings to Strabane could start this year but he expected challenges.

“This is not a procurement issue, because we have a contractor in place. However, we still have certain things to do with that contractor before he can start the next phase.

"This challenge is from the anti-A5 alliance, and there is a high likelihood that there will be another one of those challenges, probably after the public inquiry,” said Dr. Murray.

A public inquiry will consider environmental matters over four days from February 18. Other matters will be heard over three days from March 11.

The minister said that pending the outcome of this she was “hopeful that first phase of this scheme, from Newbuildings to north of Strabane (Phase 1A), could commence in late 2020/early 2021 with completion in 2023.”

Roads minister Nichola Mallon.