The Scottish Government’s insistence that it lacked the power to ensure parts of the Beauly-Denny power line were placed underground has apparently been called into question by the official report of the public inquiry.

Energy Minister Jim Mather approved the controversial 137-mile line that would cut through some of Scotland’s most scenic landscape on Wednesday, on the condition that the developers came up with ways of limiting the visual impact at certain points on the line.

The original plans were to be prepared with the local communities affected, and then presented to the minister. However, Mr Mather subsequently made clear that while these plans could include undergrounding, he did not have the power to insist at that stage.

His spokesman confirmed yesterday: “The Beauly to Denny application was made under Section 37 of the Electricity Act 1989. Under this legislation, ministers have the power to consent or reject proposals to install, and keep installed, overhead power lines. Ministers have no powers to direct that sections of electricity infrastructure be undergrounded.”

This has left many campaigners against the line wondering why so much time was spent on the issue during the 105-day public inquiry.

However, in the six-volume official report of the inquiry published on Wednesday, it appears the inquiry reporters themselves thought the minister had this power – albeit one that, if exercised, would require the developers to go back to the regulator Ofgem for permission to spend extra money.

They say: “If the Scottish Ministers required a section of the proposed line to be undergrounded, the applicants would need to revert to Ofgem with an ‘asset value adjusting event’, as the economic justification of the project would be affected.

“Based on the generic evidence at the strategy session of the inquiry, the Technical Assessor concludes that the Beauly-Denny scheme would still be the most economic scheme if a total of 10km of line was undergrounded, even with two cables per phase.”

They add: “...the economic case for reinforcing the Beauly-Denny line is so strong that a section or sections of the line could probably be undergrounded without rendering the project uneconomic.”

Thousands of objectors were opposed to the visual impact of the planned 600 huge pylons, some of which will be taller than 200ft, across the landscape and saw undergrounding as the answer for parts of the route in the Cairngorms National Park and near Stirling.

David MacLehose, chairman of Scotland Before Pylons, told The Herald the group would be seeking legal advice on this point.

He said: “It is extraordinary that the Government ministers should adopt this approach when a section of the controversial transmission line in Yorkshire 10 years ago was required on environmental grounds to be placed underground; when a high-voltage line near the Olympic Stadium in London has been installed underground on landscape grounds; and when some European Countries require cables to be undergrounded in environmentally sensitive areas.

“How can Scotland claim to set green credentials while plundering our precious natural and cultural heritage?”