A government-commissioned study is considering the feasibility of a tunnel beneath the Irish sea, linking Holyhead and Dublin, a minister has confirmed.
The news came after Liberal Democrat peer Lord Roberts of Llandudno tabled a question in Parliament.
Baroness Vere, parliamentary under-secretary of state at the Department for Transport, said that the Union Connectivity Review (UCR), independently chaired by Sir Peter Hendy, was due to give an assessment on the feasibility of a fixed transport link between Great Britain and Northern Ireland.
The Fixed Link Feasibility Study is being lead by Professor Douglas Oakervee and Professor Gordon Masterton, and focuses on the technical viability of such a construction, as well as potential costs and timescales.
Vere said: “As with any assessment at this early stage, it is important to consider the broad range of options, so a route between Holyhead and Dublin is being assessed as a comparator. Since this route is not the main focus of the study, only high-level discussions around it have taken place. These have been facilitated by the independent technical team leading the study.”
It emerged in March this year that Oakervee, former HS2 and Crossrail chairman, and Masterton had been commissioned to undertake the study, after the government resurrected plans for a bridge linking Scotland and Ireland in an attempt to boost the union after Brexit. Estimates put the cost of a bridge at £20bn. Prime minister Boris Johnson had previously floated the idea when he was foreign secretary, with possible routes including a 20-mile stretch between Portpatrick and Larne, or near Campbelltown to the Antrim coast.
But any such project involves significant challenges, including the need to build around 30 huge support towers in water up to 300m (1,000ft) deep. There are also concerns that the bridge would need to cross the Beaufort Dyke, where 1.5m tonnes of munitions were dumped in 1946 after the second world war, reportedly with no maps of their locations.
