Alister Jack says a tunnel linking Scotland and Northern Ireland would be cheaper and more weatherproof

This article is more than 6 months old

This article is more than 6 months old

The UK government could build a tunnel under the Irish Sea instead of a new bridge linking Scotland with Northern Ireland, Alister Jack, the Scottish secretary, has revealed.

Jack told MSPs on Thursday he had raised the tunnel proposal with Boris Johnson as a cheaper and more weatherproof option than a bridge over the sea.

He said he believed Johnson’s previous references to a bridge were a euphemism, and that the best crossing would be a tunnel – a theory he said the prime minister had asked UK government officials to investigate.

“It would be less expensive to tunnel it,” he told MSPs on the Scottish parliament’s culture, tourism, Europe and external affairs committee. “It’s no different to the tunnels connecting the Faroe Islands, it’s no different to the tunnels going under the fjords.”

Jack insisted there were longer tunnels in other parts of the world, and told reporters he envisaged the crossing starting as a bridge, then going under the sea for a 22-mile tunnel before rising up to be carried by a bridge again.

He said that a bridge across the entire distance could be closed for up to 100 days a year by the severe weather which can hit the Irish Sea.

His proposal was quickly ridiculed by his opponents. Ross Greer, a Scottish Green Party MSP who questioned him during the committee hearing, said: “These proposals might be headline grabbing but let’s face it, they are pure fantasy, just like the Tory approach to Brexit which Mr Jack so spectacularly failed to explain to the committee.”

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Proposals for a bridge over the Irish Sea have had support in principle from across the political spectrum, including from Mike Russell, the Scottish Brexit secretary and SNP MSP, and Arlene Foster, the Democratic Unionist party leader.

Nicola Sturgeon, the first minister, has not opposed the idea but her government was sceptical about the economic justification for sinking tens of billions of pounds into a crossing, arguing the money could be better spent on other projects.

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The leading option is to build the crossing from Portpatrick, near Stranraer in south-west Scotland, to Larne, north of Belfast, although a crossing from the Mull of Kintyre in Russell’s Argyll and Bute constituency has also been mooted.

Critics say the bridge runs the clear risk of encountering a vast dump of more than 1m tonnes of old munitions dumped in Beaufort’s Dyke, a 300-metre deep ocean trench. Jack said a tunnel could avoid disturbing the spent shells dumped there.

“Once we get better sight of the costs involved, should the prime minister decide to press the button, we would then want to engage with both [the Northern Ireland assembly and the Scottish parliament] to get a better understanding of the benefits and the challenges,” he said.

“We’re not going to just come riding roughshod and slam a tunnel in – and by the way, under the settlement of devolution, nor can we.”

Sturgeon’s spokesman told reporters after Jack’s evidence that the idea of a tunnel was news to the Scottish government. He said Michael Matheson, the Scottish transport and infrastructure secretary, had written to the UK government questioning the rationale for the project last month.

“If you’ve a spare £100bn, pick a number, it would be better off being spent in other ways, including a fair share for Scotland and Northern Ireland,” the spokesman said.