A feasibility study by the UK government has concluded that a cost of a bridge or tunnel between Northern Ireland and Scotland would be "impossible to justify".
It estimated that a bridge would cost about £335 billion (€394 billion) and a tunnel would cost £209 billion, and while both were technically possible “the benefits could not possibly outweigh the costs”.
The UK government published its technical feasibility study into a fixed link between Northern Ireland and Britain on Friday.
The study's author, Peter Hendy – who is the chairman of UK train operator Network Rail – recommended "further work on the fixed link should not progress beyond this feasibility study".
The North's Minister for Infrastructure, SDLP deputy leader Nichola Mallon, who has consistently opposed the construction of the bridge – along with her counterpart in Scotland – welcomed the study's recommendation and called on UK prime minister Boris Johnson to redirect the money for the bridge to Northern Ireland.
"It will not be a surprise to many that today's published connectivity review and feasibility on a fixed link between Northern Ireland and Scotland is recommending not to proceed," Ms Mallon said.
“It is clear that this unworkable and expensive project was nothing other than an Tory vanity project used as a distraction from the British government’s failings to invest in infrastructure here in the North.
“Alongside others in Scotland, I am calling on the prime minister to deliver his long promised investment so it can used by those of us in devolved administrations to enhance our public services to ensure we can deliver what our citizens and communities deserve,” she said.
The study assessed the technical engineering feasibility of constructing either a bridge or a tunnel between Britain and Northern Ireland and followed a 2018 suggestion by Mr Johnson that a bridge – dubbed the “Boris Bridge” – should be built between the two islands.
It concluded that while the latest engineering technology meant it was possible to construct either a bridge or tunnel, a bridge would be “the longest span bridge built to date” and the tunnel would be “the longest undersea tunnel ever built”.
The construction of either structure – and the “associated very significant works on either side for a railway and possibly for roads” – would take “a very long time”, the study found.
“Planning, design, parliamentary and legal processes, and construction would take nearly 30 years before the crossing could become operational, even given a smooth passage of funding and authority to proceed.
“Whilst the economic and social effects would be transformational, the costs would be impossible to justify.”
However, Mr Hendy said that despite his recommendation, exploring the feasibility of a bridge or tunnel link had been “an excellent question to ask”.
“For many decades, politicians and engineers have debated this proposal, but have done so without the evidence to show whether it was possible and, if so, what it would take to do it.
“This is the first comprehensive, conclusive study on the subject since the idea was first mooted over 150 years ago,” he said, adding that one day it may be possible “to satisfy the ambition to join up Great Britain and Northern Ireland at an affordable price and timescale.”
The study was published alongside the Union Connectivity Review, which considered transport infrastructure across the UK and made a number of recommendations as to how the UK government should support improved connectivity to and from Northern Ireland.