Work is under way “by a range of government officials” to look at the idea of building a Scotland-Northern Ireland bridge, Number 10 has said.
Boris Johnson has described the bridge as a “very interesting idea”, while Ireland’s premier Leo Varadkar has said it was “worth examining”.
Two routes have previously been floated – from Portpatrick to Larne or near Campbeltown to the Antrim coast.
The Portpatrick route would be more than 20 miles across the Irish Sea.
The prime minister’s spokesperson said: “The prime minister has said it would have some merit – as a result you would expect government to be looking into it.
“Work is under way by a range of government officials.”
How much could a Scotland-Northern Ireland bridge cost?
The price of any construction would, obviously, be dependent on the route chosen.
More than a decade ago the think tank the Centre for Cross Border Studies suggested a 21-mile bridge from Dumfries and Galloway could provide international rail links and ease the strain on air services.
At that time it estimated the cost of the scheme would be about £3.5bn.
However, by last year the suggested price tag had risen considerably.
Some experts have suggested £15bn might be required for the project but others have said that £20bn would be a “conservative estimate”.