- Clandon Park, an 18th century mansion, was left a charred shell after fire in 2015
A scion of the family that gifted one of the country's grandest houses to the
National Trusthas accused the charity of betraying an agreement to preserve it.
It now wants to preserve Clandon, the ancient seat of the Earls of Onslow, as a ruin with its external walls and windows restored but nearly all of its interior 'thoughtfully conserved in its fire-damaged state'.
The Trust says this will offer people 'a unique "X-ray" view of how country houses were made'.
But Constance Watson, whose grandmother Lady Teresa Waugh - daughter of the 6th Earl - lived at the mansion near Guildford, Surrey, as a child, has branded the plan a 'blatant betrayal.'
Miss Watson, a journalist, said: 'A member of the Onslow family - my ancestors - gave the mansion to the National Trust by Deed of Gift in 1956, along with an endowment of £40,500 (approximately £1.3 million in today's money).
'The deed recited that the donor 'is desirous of presenting [Clandon] to the Trust for preservation' under the National Trust Acts of 1907 and 1937. They dictate that the Trust will secure the 'permanent preservation' of buildings and land in its care.'
Restore Trust, a protest group of National Trust members, believes the Trust's plan is the latest example of it failing in its values and has raised a motion ahead of the Trust's annual general meeting in November calling for a full restoration of Clandon's interior.
Following the fire, the Trust initially said it hoped to rebuild the Grade-I listed mansion near Guildford in Surrey. It says its approach has 'evolved in response to expert assessment.'
Its revised plans, first announced last year, also include what it calls 'sensitively designed walkways and platforms' that will make the 'dramatic fire-damaged spaces' inside Clandon 'fully accessible', and a new roof with public terraces and roof lights which will it says will give 'breath-taking views' into the house and across surrounding countryside
Miss Watson, great-grand-daughter of satirical writer Evelyn Waugh, said the Trust's plan amounts to turning Clandon into 'some sort of avant-garde visitor experience'.
She added: 'The current plans are a blatant betrayal of the Deed of Gift, intended to preserve the architectural gem for the nation in perpetuity. If Clandon is not safe, where is?'