The plans were rejected by councillors by a single vote after hours of debate in December last year.

Proposals by Duddingston House Properties (DHP) would have seen the A-listed neoclassical building converted into a luxury hotel operated by five-star chain Rosewood.

Now DHP has lodged a formal planning permission appeal with the Scottish Government’s planning and environmental appeals division just before an official deadline.

A spokeswoman for the hotel consortium said: “Duddingston House Properties and the Urbanist Group can confirm that they have lodged an appeal with the Scottish Government following the decision by the City of Edinburgh Council to reject their planning application to restore the old Royal High School and create a world-class hotel to be operated by Rosewood.”

National heritage watchdog Historic Scotland had condemned proposed extensions that are central to the redevelopment, saying the wings will “dominate and overwhelm” the 200-year-old listed building.

It later emerged that the project was one of several cited in a dossier to world heritage body Unesco, which has said it is “deeply worried” over the quality of new developments in the city.

A rival plan to transform the building into a new concert hall and music school featuring three performances spaces and a 300-seat concert hall in the school’s former debating chamber has also been submitted.