Boris Johnson’s proposed bridge or tunnel to Northern Ireland could cost more than £300bn and should not be built, a government review has found.
The prime minister had commissioned a study into the fixed link across the Irish Sea after arguing it would improve connections between parts of the UK.
Network Rail chairman Peter Hendy’s review found that that a bridge would cost an estimated £335bn, while a tunnel would be about £209bn.
Sir Peter said the high price tag of either project “would be impossible to justify” as “the benefits could not possibly outweigh the costs”.
Either a bridge or tunnel would be the longest of their kind ever built.
Various proposals have been made for a fixed link between Great Britain and the island of Ireland since Victorian times but none have got past the drawing board.
Sir Peter said despite his recommendation the prime minister had asked an “excellent” question by proposing the bridge or tunnel.
The Network Rail boss’s review, which looked at wider connectivity across the UK, also recommended a series of improvements to road and rail across the country.
He said the north Wales mainline should be electrified and that improvements should be made to the West Coast main line north of Crewe.
The latter project could cut journey times from London to Scotland to below three hours and trigger a shift in passengers from air to rail on the route, he said.
Sir Peter also said the government should establish “UKNet” a network of strategic routes across the UK. He argued the government should provide funding to make sure all the network’s designated corridors were up to scratch.
The prime minister pledged to set up UKNet “right away”.
“If we want to truly level up the country then it’s vital that we improve connectivity between all corners of the UK, making it easier for more people to get to more places, more quickly,” he said.
“Sir Peter Hendy’s review is an inspiring vision for the future of transport which we will now consider carefully.
“Determined to get to work right away, we will set up a strategic UK-wide transport network that can better serve the whole country with stronger sea, rail and road links – not only bringing us closer together, but boosting jobs, prosperity and opportunity.”