Boris Johnson gave his blessing to a magazine exploring a multibillion pound rail tunnel between Scotland and Northern Ireland.
Sir Peter Hendy, Chairman of Network Rail, has asked experts to conduct a review of a potential tunnel between Stranraer and Larne.
Doug Oakervee, the author of a government-commissioned report that gave the green light to HS2 earlier this year, will lead the analysis.
Sir Peter said: “If you look at the distance between Northern Ireland and Scotland it is actually no further than the Channel Tunnel.
“I told Boris, I’m not going to go beyond whether it’s doable, how long it will take and how much it could cost. “
The Prime Minister tasked Sir Peter to conduct a wider ‘Union Connectivity Review’ in June to assess improvements in transport links between England, Scotland, Wales and Wales. North Ireland.
Last September, Mr Johnson asked officials to consider building a 21-mile bridge between Northern Ireland and the mainland at an estimated cost of £ 20 billion.
Scottish ministers said in March that Downing Street had now asked them to watch a tunnel amid fears high winds could close a bridge for up to 100 days a year.
A key part of the Convervatives’ commitment in the general elections to level the economy was to boost regional connectivity.
Fears grew, however, that the coronavirus pandemic had put that priority on hold – especially when ministers refused to bail out regional airline Flybe in March.
Sir Peter, who ran Transport for London under Mr Johnson when he was Mayor of London, told the Railway Industry Association’s annual conference: “Government policy is to bring the UK together. The pursuit of economic growth, especially in the light of Brexit, is a shared will of Westminster and developed governments.
“If you look at the air and ferry connections, one of the current problems for Northern Ireland is that since Flybe went bankrupt there are far fewer possibilities to fly in Northern Ireland. They clearly find it very difficult. Maybe I can look at this and do something about it.