Holmes Partnership, one of Scotland's most respected practices, was chosen from a shortlist of five by a council selection panel.

The practice, which has offices in Glasgow and Edinburgh, will act as lead consultant on the Marischal Project, as part of a team comprising Arup Scotland as the civil and structural engineer and Wallace Whittle as building services engineer.

Marischal College, designed by A Marshall Mackenzie and Archibald Simpson, is a structure of national significance and the second largest granite building in the world.

The scheme will involve the demolition of the Marischal College interior, which will be replaced by a 21st century office building providing 174,000 sq ft of modern office space over four floors for up to 1,300 city council staff.

The conversion will create some 200 parking spaces, ensure the retention of all the granite elevations, and provide a new, predominantly open-plan interior of contemporary, hi-tech and sustainable design.

Aberdeen City Council leader Councillor Kate Dean said: "The appointment of these firms, who are among the leaders in their fields, puts in place a real A-Team worthy of converting our A-listed Marischal College.

"Aberdeen deserves the best for its best building. I believe we have signed up architects, engineers, project managers and quantity surveyors who are as excited and as enthusiastic as we at the council are about completing this unique project."

It is expected that staff will move into the new building during the first quarter of 2011.