As decision day looms for the controversial scheme, Norwich Society has sent a scathing critique of the scheme to Norwich City Council.
It also calls for people to make their opposition public.
The Society said the planning application by Weston Homes - including 1,250 flats, a 200-bed hotel and a 20-storey tower - was 'the most serious threat to the character and long-term economy' Norwich had seen for many years.
It asks for the support of several big names, including Mr Fry, architect Sir Michael Hopkins and national charity Civic Voice.
Locally, it is appealing to Epic Studios, Maddermarket Theatre and Open to sign the letter, and already has the support of Historic England and campaign group Angrier Square.
The letter will be sent to all city councillors ahead of their December 6 meeting, when a decision will be made.
It raises fears that Norwich could become 'yet another clone city' and outlines concerns about the proposed tower block spoiling the city skyline.
It also argues the proposed 1,250 new flats and 200-bed hotel would mean the area exceeded the recommended density for an urban area in London.
Weston Homes defended the development and said there would be many 'positive effects', such as framed views towards St Augustine's Church tower from Anglia Square along Botolph Street.
The company has already spent £3.5m on planning and consultation and said it made substantial changes to its initial application, including cutting the controversial tower from 25 stories to 20.
Norwich Society has a 90-year history of fighting for the preservation of the city's historic architecture, including blocking demolition of Tudor housing on Elm Hill and the destruction of Bishop's Bridge.
Norwich Society chairman Vanessa Trevelyan said the society agreed the area needed redevelopment but it should be done in a way that was sensitive to its existing neighbours and attractive to new entrepreneurs and businesses.
Mrs Trevelyan added: 'We don't want the city to be stuck in the past and we welcome development and design which blend in nicely with the historic architecture.
'We need a development which reflects our thriving 21st century city and celebrates its roots, which are rich in heritage.'
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