Duddingston House Properties (DHP) and the Urbanist Group are to launch a pre-planning application next month to convert the old Royal High School on Calton Hill.

Along with institutional investors, they have raised more than £55 million for the project.

Initially considered as a possible site for the Scottish Parliament, the Thomas Hamilton designed former boys’ school opened in 1829 but has remained empty since 1968.

The City of Edinburgh Council, which owns the A-listed building, granted DHP a 125-year conditional ground lease after the company won an open competition in 2010.

The developers said several unnamed hotel operators had been shortlisted as frontrunners to manage the new hotel, if permission is granted.

They added that the hotel was “likely” to create 640 local jobs and contribute an average of £27m annually to Edinburgh’s GDP.

David Orr, of the Urbanist Group, said: “What we are proposing to do is to add something truly special to the Edinburgh hotel market by bringing one of the best hotel operators in the world to the city.

“This will not in any way diminish current hotel provision; indeed it will add another tier at the top which can only benefit all of the city’s operators.

“By increasing the breadth of hotel offering, Scotland’s capital will be in a position to attract new visitors from the top end of the market as well as improve its ability to compete with other European cities for international diplomatic events and important global conferences.

“But importantly, one of Edinburgh’s architectural jewels in the crown will be sensitively restored and the public will have access to Hamilton’s superb building for the first time.”

The project is pushed by DHP chief executive Bruce Hare, architect Gareth Hoskins, and the Urbanist group.

The developers are due to submit a Proposal of Application Notice (PAN) to the council in January, followed by three days of public consultations at the old Royal High School in February.