A conservation officer has said historic Burton Hill House School in Malmesbury could be subjected to ‘harmful alterations’ if proposals to convert it into seven residential units receives planning permission.

Developer Tansette Ltd is hoping to receive approval for its plans at a Northern area planning committee meeting on Wednesday.

But the Grade II listed building is in danger of being spoiled, according to Wiltshire Council conservation officer Caroline Ridgwell.

In a damning letter to planning officers she criticises the proposals and suggests they be refused.

In particular she says that, despite detailed negotiations, the developers have largely failed to address concerns raised over design and alterations to the building and surrounding area.

She is critical of how developers plan to subdivide the historic rooms and describes the creation of a vehicle access and construction of a double garage on the site’s principal elevation as ‘extremely harmful’.

The landmark building, rebuilt in 1846 following a fire and designed by Charles Cockerell who also created Oxford’s Ashmolean Museum, was sold for £2 million last year. Since 1947 it had been used by the Shaftesbury Society as a residential school for disabled children and also housed evacuees during the war.

Summing up Mrs Ridgwell said: “The proposed scheme lacks vital information and shows a generally unsympathetic approach to the change of use of this building.

“The proposed work will result in extremely harmful alterations to this listed building and the permanent loss of historic floor plans and landscape.

“This will be detrimental to the character, appearance and setting of the listed building, it’s curtilage and the amenity of the area.

“I recommend refusal.”

However, town councillor Charles Vernon of the Malmesbury Civic Trust, who was instrumental in securing listed building status for the school, said the revamp would keep the structure from falling into disrepair.

He said: “We have great interest in the house.

“Since the time it was built it has changed.

“A ballroom was added and it has been used as a school for 60 years.

“It is really important that the internal features of the building be retained and we felt the proposals put forward largely did that.

“Any other use, such as a hotel, may not.”

The 15-acre site includes landscaped gardens, a lake and mature woodland.