The Telegraph disclosed on Monday that experts advised Scottish ministers to move out of its St Andrew’s House headquarters in Edinburgh because the changes would be so expensive and difficult to implement.

The assessment of Bute House was conducted by the same company, Hollis, an international real estate consultancy. It was obtained by The Telegraph under Freedom of Information legislation.

“Due to the size of the building, we recommend direct electric heating will be the most appropriate heating replacement in lieu of gas,” it said.

“We have excluded ASHP [air source heat pumps] due to the Grade A [National Trust] status.” It noted that the work would likely require listed building consent and the permission of the National Trust for Scotland.

It said that the “indicative” £807,038 cost included the cost of switching to electricity for heating both the property and its water supply.

Decarbonisation support ‘woefully inadequate’

Maurice Golden, a Scottish Tory MSP, said: “The SNP Government have set aside a woefully inadequate sum to decarbonise the heating of one million homes.

“As it stands, this funding will only go a fraction of the way to decarbonising many Scottish homes, leaving homeowners to make up the difference from their own pockets.

“If the SNP are to have any hope of reaching their decarbonisation targets, they must commit to properly funding homeowners to make the necessary improvements.”

A Scottish Government spokesman said: “Our draft Heat in Buildings Strategy sets out our vision for transforming more than one million homes and an estimated 50,000 non-domestic buildings to be using low- and zero-emissions heating systems by 2030.

“We are supporting this with a groundbreaking £1.8 billion investment to transform heat and energy efficiency of buildings, rapidly accelerating the decarbonisation of an area which makes up a quarter of Scotland’s greenhouse gas emissions.”