Minto House, near Hawick in the Borders, which was already in a dilapidated state, was badly damaged when workmen set it alight as a preliminary to demolition on Thursday.
As the flames spread from the vaults of the 64-room mansion Ian Lang, Secretary of State for Scotland, broke off his holiday to authorise the granting of Category A listed status.
The move, which followed lobbying by conservation groups, halted the demolition ordered by Lord Minto, the house's owner, after he had been unable to find a buyer for his ancestral home.
The house, which was remodelled by James Adam in 1738 and which has been unoccupied for 26 years, was to have been moved stone by stone to Japan but the deal fell through recently.
Yesterday, site meetings between Lord Minto and planning officials from the Scottish Office and the regional council revealed a conflict between safety regulations and conservation rules in the case. Afterwards he said: 'I have been advised that it would be unrealistic to try to make the structure safe and that the correct course is to proceed immediately with the interrupted demolition.'
Douglas Connell, Lord Minto's lawyer, said: 'The advice that is coming from building control officials, who have got to look at public safety, is that demolition is the option that should be pursued as soon as possible.'
He said that public safety regulations took precedence over conservation controls and that it would not be necessary to have the Category A listing lifted before knocking the house down.
Lord Minto, convenor of the Borders Regional Council, which is the planning authority in the case, said he would put a guard on the house over the weekend and meet officials again on Monday. But Jenny Hess, spokeswoman for Historic Scotland, the body responsible for looking after listed buildings, said that Minto House could not be totally demolished. 'The position is that listed building legislation still applies. The building control people have to satisfy Historic Scotland that any demolition is the minimum required to make the building safe.'
Marianne Watson-Smyth, secretary of Save Britain's Heritage (Save), a conservation group which asked Mr Lang to intervene, said: 'If the building is dangerous it can be fenced off.
'What we think Lord Minto should do is find a new use for the building and a new owner. We do not feel that he has explored every avenue and we believe the house could have a future even though it is very decayed.'
Two years ago Save published a report which said that 140 large country houses in Scotland were in danger of collapse. Some have since been restored but most are still in danger.