The glut of City bonuses over Christmas and the new year period has led to many top earners spending their windfalls on status symbols such as listed country retreats.
But listed properties are subject to extremely strict planning and building controls, with local authorities insisting that any damage is repaired to a certain required standard.
This means costs can far exceed market value, with specialised tradespeople needed to repair or renovate features such as carvings, mouldings, timberwork or specialised decorations.
A typical modern property costs 1,200 per square metre to rebuild whereas a listed property could cost upwards of 4,000 per square metre.
Tim Price, corporate communications executive at NFU Mutual, says: “It is shocking to realise that one in four owners of the most prized properties in the country are without adequate cover.
“Owning a listed property is a pleasure and a responsibility, but if you are underinsured it can be a major headache.”
A recent white paper by Tessa Jowell, secretary of state for culture, media and sport, means home owners will now be informed if their properties are to be listed. Previously, decisions by English Heritage were kept secret.
This will mean that if informed owners attempt to change or destroy special features of their houses they could be subject to a 20,000 fine or even a jail sentence.