A fierce battle has broken out to save the site of a Jacobean mansion from a new housing development that offers buyers integral garages, balconies and all the joys of 21st-century living - but at the expense, say conservationists, of one of Scotland's architectural gems.

For much of the last century Nisbet House, near Duns, lay rotting and derelict, until 2000 when it was bought by Magnus and Georgie Laird. The couple poured all their money and time into Nisbet and, in a labour of love that might delight the producers of television's Grand Designs, they recast the dilapidated Grade-A listed house into a home.

In just one month, the prospects for Nisbet have been transformed. To the Lairds' disbelief, a development plan has emerged for a strip of land metres from its east facade.

The scheme, approved by Scottish Borders Council, permits the construction of two 8.5m-high (28ft), two- storey houses - vilified as a “generic, nowhere design” by one architectural heritage body - in the heart of a group of grade-A listed structures.

The Lairds only found out about the proposal at the completion of a four-month planning process that they had known nothing about. “It's difficult not to personalise it when it is your home,” said Mr Laird. “But it is the bigger picture that outrages me more. This is not just a private house, it has a place in the national heritage.”

His anguish has been intensified by the inability of Historic Scotland, the government agency charged with defending the country's built heritage, to halt or even influence the appearance of the new development, despite raising concerns with the council about “certain aspects of the design”.

Mr Laird said: “You would have thought that Borders council would care about a place like this, that the planners would care. Apparently they don't and Historic Scotland has been ignored at a local planning level.”

At stake is the site of a mansion built in the early 17th century by Alexander Nisbet of that Ilk, who bankrupted himself in the Royalist cause during the wars of the 1640s and 1650s.The impressive tower at the west end was added in 1774 and probably designed by the architect William Adam. Though much of the surrounding estate has been lost to farmland, a dovecote and a walled garden are mementoes of its former grandeur.

David Finnie is the local builder who hopes to construct the new houses on the strip of ground owned by a farmer that lies at the heart of the group of structures that form Nisbet.

Mr Finnie accuses Mr Laird of seeking to buy the strip at a knockdown price, so that he can develop it for himself. The charge is batted away by Mr Laird, who said: “The land only has value if it is seen as development land. I have no intention of developing anything. This is all about defending an historic site,” he said.

More worryingly for the owners of Nisbet is the fact that Mr Finnie has demonstrably followed most of the planning rules, aside from the question of notification, which is disputed. “We had a development officer who came and gave us his input. He said we should ‘go contemporary' or do it in keeping,” said Mr Finnie. “We followed his advice. We knew there would be issues but we went through the correct planning procedure.”

Much of this was true, Mr Laird said, but with hundreds of square miles of empty land in the Borders, and with the town of Duns nearby, he wondered why it was necessary to build at all in the midst of an unspoilt group of 17th and 18th century buildings. It is a cry that has been taken up by a number of influential supporters. The Scottish Civic Trust, the Architectural Heritage Society of Scotland (AHSS) and Berwickshire Civic Society have written to Scottish Borders Council objecting in the strongest terms to the new development. The Georgian Society, an English body, felt moved to comment on a Scottish building “because of the importance of Nisbet”.

By contrast, the two planned houses, according to the AHSS, have a “nowhere design” that makes them “completely inappropriate to the location”.

A final decision on the scheme will be taken at an area planning committee meeting next month.

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