TV antiques show expert John Bly warns Prince Charles of risk to treasures

John Bly, who appears on the BBC programme Antiques Roadshow as its furniture expert, said the unique items at Dumfries House in Ayrshire had started cracking and shrinking because managers had failed to look after them properly.

He said he was concerned the prince's advisers could employ conservers who would ruin "untouched masterpieces" by over-restoring them and making them look like new shop items.

Dumfries House trustees rejected the claims and said Mr Bly had not even seen the pieces that had been restored.

Prince Charles used 20m of his charities' cash to buy the country house in 2007 from the Marquess of Bute. Some of the furniture, such as a Chippendale rosewood bookcase made for Lady Dumfries' bedroom during the reign of George II, could be worth as much as 4m.

Mr Bly said he was like a "kid in a sweet shop" when he visited the house with the Antiques Roadshow in September last year and first saw the collection.

But after a return visit this summer, he said he was shocked at the deterioration of some of the furniture, and wrote a strongly worded letter in August to the prince's advisers. He said the reply he received totally failed to answer his concerns.

He said: "What they are doing at that house is misguided, in my view. There's misplaced energy and experience.

"Damage manifests itself in cracking and distortion of veneer due to timber shrinkage. This has been caused by a lack of circulation of air.

"We are in summer and the house is over-warm ,and yet apparently, the windows are now permanently closed.

The furniture needs to breathe, as it has been allowed to do throughout the preceding centuries."

A spokesman for Prince Charles and trustees of Dumfries House said the claims were "completely unfounded".

Sir Hugh Roberts, one of the trustees of the charity which owns Dumfries House, said he was absolutely satisfied with the rigorous and cautious approach taken to the furniture.

Sir Hugh, the former director of the Royal Collection and Surveyor of the Queens' Works of Art and an internationally known expert in the furniture and interior decoration of the 18th and 19th centuries, said: "Nothing that is being done in any way supports Mr Bly's view that we are damaging the great collection in the house.

"We are protecting and conserving it for future generations to enjoy, and if Mr Bly were to come and see the first pieces of furniture we have conserved, which I believe he hasn't, I am confident he would be reassured that these Chippendale masterpieces are in safe hands."

Mahogany and veneered furniture are being conserved by Arlington Conservation, according to Sir Hugh.

A spokesman for Charles said: "The Prince is delighted with the progress of the conservation work, which is being done to the highest possible standard."