The heritage quango has slammed plans by local developer Bill Gredley - a member of the Sunday Timesrich list - to build an art gallery and hotel on land currently occupied by grade II-listed stables.
Using his in-house architecture team, the local entrepreneur has submitted plans for Queensbury Lodge stables, that won the backing of town councillors in Newmarket on 20 March, despite the protestations of EH.
If the project goes ahead it will see the incorporation of elements of the listed building complex into the new scheme.
But EH's concerns can still be used as ammunition by another planning authority, Forest Heath District Council, which also has to approve the scheme.
An EH spokesperson said that while it was keen to see the stables brought back into use, it was 'extremely concerned' about the level of alterations proposed to the listed buildings.
The spokesperson added: 'We have met with developers on site to talk through some possibilities and to explain that the proposed changes would detract from the special interest and character of individual buildings and the site as a whole.'
Gredley has made a number of attempts over the last 20 years to redevelop the stables, despite the protestations of local heritage campaigners.