National heritage experts are not happy about "intrusive" plans for a "tortoise house" at historic Melbourne Hall.

The Hall, six miles from Ashby, is listed as Grade-II* and its grounds, including the gardens, are listed as Grade-I – the highest level of important and associated protection.

As a result, Historic England is keen to avoid any potential detraction or detrimental effects on the gardens, grounds and hall itself.

It has formally objected to retrospective plans from the hall for a tortoise house in the stable complex, close to the gardens, fearing it would be "intrusive" and the start of further potentially harmful development on structures of "exceptional historic interest".

The hall, which has already built the "house" for rare giant tortoises as an extension to existing stables buildings, plans to gain a formal zoo licence.

This licence, and the existing animals, are aimed at drawing more people to visit the hall estate, ensuring that it can be maintained for future generations, it says.

The hall is already home to: Pigs, pygmy goats, rare breed Portland sheep, rare breed Suri alpacas, miniature ponies, rabbits, guinea pigs, chickens and numerous ornamental duck breeds.

It stresses that the tortoise house is not yet open or accessible for the public and that it will issue updates when the time comes that visitors can come and see the rare reptiles.

Historic England, in its objection letter to retrospective plans to build the existing tortoise house, says: "The application documents are not clear on whether giant tortoises are the only new animals proposed to be introduced, and whether changes to current fencing arrangements, surfacing or other aspects of the garden landscape are proposed.

"The heritage statement does not provide an adequate, or proportionate, assessment of the historic significance and heritage impacts of the proposals, particularly given the very high significance of the heritage assets at Melbourne Hall.

"The further extension of the existing stables building, including the addition of a tortoise house, would continue to assert an estate character in an important area of the formal gardens at Melbourne Hall. Further extension of the building into the central vista from the Four Seasons Vase, would make them intrusive in a key historic view.

"The proposals will result in a harmful impact on the character of the registered park and garden, and make the stables building more intrusive in views down the central vista from the Four Seasons Statue.

"They would not enhance the historic character and significance of the gardens and may result in erosion of the historic character of this part of the gardens.

"Historic England therefore has strong concerns regarding the heritage impact of the proposals.

"Melbourne Hall, its park and garden, and the collection of statutory and other buildings within it are of the highest historic, architectural and artistic interest.

"The authority will need to consider whether there is a clear and convincing justification for the proposals, and sufficient public benefit to outweigh the harm."

A statement from TUK Architecture, on behalf of the hall estate, says the paddocks and stables at Melbourne Hall were built 30 years ago and "diversification" – changing of business use – started five years ago.

It says: "The decision to diversify the gardens of Melbourne Hall is partially financially motivated.

"Over recent years, the income generated from the gardens does not cover the cost of ongoing maintenance, or even the wages of the staff required to keep the gardens in their current condition.

"As such, it is absolutely imperative for the future of the gardens that additional revenues are established.

"It is also important to note that Melbourne Hall is home to the Kerr Family, who have always been passionate about animals and gardening.

"They want to share their pets with the wider community. It's a fantastic collection of rare breed animals, for the enjoyment of so many families in South Derbyshire.

"The aim of the zoo is also to widen the appeal of the gardens to prospective visitors, to attract younger visitors, and families.

"The animals can be seen within their paddocks, and fed with feed purchased at the entrance by visitors, every day that the gardens are open – excluding the tortoises which are not presently available for public viewing.

"By appealing to a broader audience it is hoped that this will increase the revenue generated for the estate, it also increases the public benefit of the privately owned heritage asset.

"The location of the paddocks and zoo were also carefully selected, sited away from all of the Grade-I listed features of great heritage value.

"The structures and paddocks are entirely masked from view of the nearby Four Seasons Vase.

"There are currently no plans to introduce any other animals, or make changes to the current fencing arrangements, surfacing or other aspects of the garden landscape."

South Derbyshire District Council is due to decide on the retrospective plans at a meeting on Tuesday, July 26, with planning officers recommending approval.

Officers wrote: The zoo/animal sanctuary is part of the wider offer open to the public as part of a visit to the historic park and gardens, which in turn generates income which allows the estate to remain financially viable and carry out the ongoing care and maintenance of the historic assets.

"It is considered that the harm to the Grade-I listed registered park and gardens and the other listed structures lying within it is less than substantial and outweighed by the contribution made to the visitor experience to the hall and gardens, which in turn provides a revenue stream which facilitates the wider conservation of the heritage assets."