Scottish Secretary Alister Jack has said he favours the building of a tunnel between Scotland and Northern Ireland – and claims Boris Johnson is “on the same page”.

Downing Street did not rule out that the Prime Minister is mulling the underground alternative instead of a previously proposed bridge.

The PM has said that serious consideration was being given to constructing a bridge between Portpatrick and Larne, but critics raised numerous problems with the idea.

Mr Jack told an evidence session in the Scottish Parliament that a tunnel would not face the same problems from the Second World War munitions dump at Beaufort’s Dyke in the Irish Sea.

When asked by SNP MSP Kenneth Gibson about the idea of a bridge, Mr Jack said: “I’m very keen on it now, but it’s not a bridge that I’m keen on, it’s a tunnel.

“It’s no different to the tunnels connecting the Faroes, it’s not different to the tunnels underneath the fjords, and it deals with the problem of Beaufort’s Dyke and the World War Two munitions.

“The bridge for me is a euphemism for a link, which is a tunnel.”

Speaking to journalists after his appearance before Holyrood’s Culture, Tourism, Europe and External Affairs Committee, Mr Jack said it could even be the case that a crossing is made up of sections of both bridge and tunnel.

He added: “But I think the best solution if we’re going to bridge Scotland with Northern Ireland is a tunnel, and I’ve had conversations along those lines with the Prime Minister.”

Prime Minister’s Questions
A spokesman for Prime Minister Boris Johnson told journalists in February about the possibility of the bridge (Stefan Rousseau/PA)

Mr Jack also said he and the PM are “on exactly the same page” when it comes to the idea of an underwater crossing.

According to the Scottish Secretary, he has been told by a number of engineers that a tunnel would cost less than a bridge.

Mr Jack described the plans as being in the “discussion phase”, and it would be for the Prime Minister to “push the button” and move forward with a full feasibility study to test if the proposals are possible.

When the initial plans were made public, the Scottish and Northern Irish transport secretaries wrote to the Prime Minister and called for the estimated £20 billion cost to instead be given to the devolved administrations to improve infrastructure – a position First Minister Nicola Sturgeon agreed with.

Mr Jack refused to reveal any costings he had been quoted for the crossing, but did say it would be “quite achievable” to have the tunnel built by 2030, adding: “Since the Channel Tunnel, costs have come down and techniques have improved dramatically.

“The problem is not about whether or not it’s feasible, it’s about how quickly you do it… If you’re going to do it you should get on and do it.”

The Prime Minister’s official spokesman was later asked whether Mr Johnson now favours the idea of a tunnel.

“His aim throughout has been to improve connectivity and we commissioned work on how best to achieve that,” the spokesman said.

Scottish Transport Secretary Michael Matheson said: ““This £20 billion vanity project by the Tories would be better spent on focusing projects that will boost our economy and connectivity and supporting our communities to reduce emissions to net zero.

“Given transport is totally devolved, there are a number of proposals already on the table which would improve connectivity between the north of Ireland and Scotland, without the technical and logistical challenges involved in this proposal, and which we could develop if there is £20 billion available to us.

“By spending just a fraction of the cost of this bridge, I believe we could bring significantly more benefits to the people of Scotland and Northern Ireland, making a real difference to improving lives.”