Alan Dunlop, visiting professor of architecture at Robert Gordon University in Aberdeen and Liverpool University, claimed a combined road and rail crossing between Portpatrick in Dumfries and Galloway and Larne in Nothern Ireland would cost around £20bn.
His comments come after foreign secretary Boris Johnson reportedly raised the possibility of building a bridge from England to France.
Connecting Scotland and Ireland by bridge has interested engineers, architects and politicians for more than 100 years.
Today, Mr Dunlop said such a structure could help tackle disputes over any post-Brexit Irish border and boost the economies of the ‘true North’.
Mr Dunlop, in an interview with The National newspaper, said: “To propose a bridge between Scotland and Ireland would be a big step in creating a Celtic Powerhouse and give politicians the opportunity to invest in the infrastructure of the true North.”
He added: “Brexit is an interesting wrinkle as a bridge might help with the debate about customs, borders and access to the European market.”
Mr Dunlop said the setting of a bridge between Portpatrick and Larne would be “more dramatic” than a crossing between Mull of Kintyre and Torr, although this would be a cheaper option.
The architect told the newspaper: “You could potentially see it from Whitehaven, the Lake District and the Isle of Man.
“While much more costly because of the geological and environmental challenges, it would also reinvigorate the area around Stranraer and potentially the whole Ayrshire coast from Troon to Stranraer and the whole north coastline of the Solway Firth for people coming from the North of England.
“I would estimate that option to cost about £15-20 billion as a conservative estimate.”
Dunlop said a bridge between Scotland and Ireland was more achievable than Johnson’s idea.
While the network of shipping lanes in the Channel pose an immediate obstacle to any such crossing, the challenges of building a bridge between Scotland and Northern Ireland are far fewer, it is understood.
The architect said the Oresund bridge which connects Denmark and Sweden could be a useful model for any crossing between Portpatrick and Larne.
The distance between the two points is around 28 miles as the crow flies.
However, a bridge here would have to overcome the obstacle of Beaufort’s Dyke, a 200-metre deep sea trench off the Scottish coast.
In 2015, East Antrim MP Sammy Wilson, of the DUP, compared the importance of building a fixed crossing over the North Channel of the Irish Sea to the high-speed rail project underway in the south of England.
A 2007 report by the Centre for Cross Border Studies estimated building a bridge from Galloway to Ulster would cost £3.5 billion.