Fettes College, which is said to have inspired JK Rowling to dream up her gothic vision of Hogwarts, is having to turn away girls because of a lack of boarding accommodation.

But a proposed £3 million development, which would accommodate up to 60 girls, has been criticised for harming the view of the 1870 building, designed by David Bryce.

Edinburgh’s main heritage watchdog is trying to block plans for the modern three-storey building, which would replace four small staff houses to the west of the main Bryce building.

The Cockburn Association has warned the city council that the scheme is too prominent for the site and prove “highly damaging” to the A-listed landmark and its historic grounds.

Fettes boasts several Victorian and Edwardian boarding houses, to the south and east of the main building, although one modern one was created four years ago, near East Fettes Avenue. All are shielded by mature trees.

Glasgow-based architects Park and Park – whose projects have included the Maggies Centre in Inverness, the Lighthouse Centre in Glasgow, and the Lomond Shores complex at Loch Lomond – drew up the plans for the proposed new Fettes boarding house.

But the Cockburn Association said it was “very concerned” about the plans and has demanded that the proposed boarding house is moved to another part of the grounds.

Marion Williams, the group’s director, said: “The existing Victorian and Edwardian boarding houses to the south of the main school building are all located within clearings in the trees and as such do not impact on the setting of the school or grounds in a significant way.

“It is most important that this approach should continue in the future.

“We believe that the design proposed and its setting in the landscape is highly damaging to the category A-listed building and the environs in which it is placed. We strongly object to these applications being granted permission in their present form.”