The organisation - perhaps the most influential of the amenity groups - has released details of a letter it sent EH at the end of October.
The campaign, which objects to the proposed changes to the house and its surrounding gardens in the strongest possible terms, aimed to influence a meeting that took place on Wednesday.
The meeting is understood to have been an opportunity for EH to persuade a number of local groups and campaigners that the proposals for the site are worthwhile and will leave the historic gardens and William Kent's Grade I-listed house unharmed.
But the plans - which include a new café by Michael Hopkins in close proximity to the house and a series of 'regeneration' projects in the gardens - have drawn fire from the Georgian Group.
The scheme would also involve the construction of a new function block very near the house and the erection of a 'temporary marquee' for events similarly close.
Unsurprisingly, many of the scheme's aspects have triggered significant frustration from Georgian campaigners. In a letter to EH, the group's secretary Robert Bargery slammed the proposals as they stand.
'At present, a project that should be founded on sound principles and be a beacon by virtue of its attention to core conservation objectives is being pushed along by expediency.
'As a result, potential solutions are blocked, things are back to front and the house is being thought about last. That is our central concern.
'We believe that a better solution - one that fully respects the house and its historic landscape while also taking account of revenue requirements - is achievable,' the letter adds.