Criticism of Classicist Simpson's proposals for the area's 'industrial middle' sector has come from both English Heritage and the Birmingham Civic Society.
Both heritage groups have issued warnings against changing the type of buildings in the area through redevelopment, from industrial space, to houses, offices and shops.
The concerns have been prompted by the planned relocation of AE Harris, one of the city's oldest metal-working firms. Its plans to redevelop its current site are currently being considered by Birmingham City Council.
Civic Society chairman Stephen Hartland told the AJ that he did not object to Simpson's designs, only the precedent set by a change in use to residential in a traditionally industrial part of the city.
In a letter to the council in May, English Heritage spokesman Michael Taylor echoed this sentiment. He said: 'The development represents a clear breach of policy 2.2 of the Jewellery Management Plan. We have seen no evidence to dissuade us from our consistent support of that policy.
'If housing is approved in any form it is bound to increase hopes of further breaches of policy and put pressure on land values in the industrial middle and golden triangle localities.'
John Simpson & Partners was unavailable for comment at the time of going to press.