The Scottish Transport Secretary has accused the UK Government of a "power grab" over plans to build a tunnel or a bridge connecting Scotland and Northern Ireland.
A major review is assessing the feasibility connecting the two countries.
SNP minister Michael Matheson criticised the report saying it was weak and that it was set up without consulting the devolved administrations.
The research is being carried out as part of Prime Minister Boris Johnson's bid to improve UK transport links.
Network Rail chairman Sir Peter Hendy, who is carrying out a review of union connectivity, said further work is required on the possibility of a "fixed link" across the Irish Sea.
Some £20 million has also been committed to develop plans for upgraded rail, road, sea and air links - and explore new requirements to offset emissions and decarbonise aviation.
Speaking on Good Morning Scotland, Matheson said: "I think it's a report which I think is actually very weak, it doesn't really tell us anything new.
"It was also a review that was set up without consulting the devolved nations Scotland, Wales, Northern Ireland.
"All of my counterparts in other parts of the UK objected to the way in which the UK government are going about doing this given that major parts of transport infrastructure are devolved matters.
"The way in which the UK Government have taken it forward is more about a power grab, and the most recent example of trying to undermine the devolved settlement, and the decision makings of the Scottish Parliament on key transport infrastructure.
"It's nothing more than a vanity project for Boris Johnson. It's not a priority for Scotland or for Northern Ireland.
"They are looking to dictate the terms of what those priorities should be because it suits them to do so. They want us to ignore everything else just to focus on their priorities."
Transport Secretary Grant Shapps has confirmed the Government is looking at the possibility of building a bridge or tunnel between Scotland and Northern Ireland as part of its review of connectivity within the UK.
Shapps told BBC Breakfast: "One of the elements in that review is should we have some sort of fixed connection - that could be a tunnel, it could be a bridge - between, for example, Scotland and Northern Ireland which is the closest crossing.
"Actually it is odd in a sense that we don't have a connection with another part of the United Kingdom so it is looking at whether that is feasible or not."
