Boris Johnson has quietly dropped plans for a £20 billion bridge between Scotland and Northern Ireland and has instead ordered officials to explore the possibility of a tunnel.
The prime minister is said to have asked experts to look at constructing a railway tunnel from Stranraer to Larne.
Doug Oakervee, author of a Government-commissioned report that gave HS2 the green light earlier this year, is reported to be leading the analysis.
Sir Peter Hendy, chairman of Net work Rail, told the Telegraph: “If you look at the distance between Northern Ireland and Scotland it is actually no further than the Channel Tunnel.
“I said to Boris, I am not going to get any further than finding out whether it is feasible, how long it will take and how much it might cost.”
Mr Johnson first floated the idea of a bridge in an interview in 2018, saying: “What we need to do is build a bridge between our islands. Why don’t we? Why don’t we?”
In June, the prime minister asked Sir Peter to conduct a “union connectivity review” to improve transport links in England, Scotland, Wales and Northern Ireland.
Last September Mr Johnson asked his civil servants to consider the building of a 21-mile bridge between Northern Ireland and the British mainland at an estimated cost of £20 billion.
There had been concerns expressed over the viability of the plan however, given the bridge would have to traverse a Second World War munitions dump.
Sir Peter, who led Transport for London under Mr Johnson when he was mayor, added: “The government’s policy is to bring the UK closer together.
“The quest for economic growth, particularly in the light of Brexit, is a common desire for Westminster and for the developed administration governments.”
“If you look at air and ferry connections, one of the current bugbears for Northern Ireland is that since Flybe went bust there is much less opportunity to fly into Northern Ireland. They clearly find that difficult. Maybe I can look at that and do something about it.”