Scottish Natural Heritage could be sued for £150,000 damages amid claims it left a famous Loch Lomond island looking like a ‘wasteland’ by deliberately poisoning and killing hundreds of ancient beech trees.

Luss Estates, which owns Inchtavannach, has accused the quango of ‘environmental vandalism’ by injecting 300-year-old trees with poison during an operation to remove rhododendron and beech saplings and to gradually fell mature beech trees.

However, the estate says that, instead, SNH decided to ring-bark and poison hundreds of beech trees all at the same time, without consulting them.

Its lawyers say this was a clear breach of any consent to them carrying out work on the island and the poisoning of the trees was ‘entirely unauthorised’.

Luss Estates, which owns the island, said SNH had created a canopy of dead trees which were a‘major eyesore’ in one of the Scotland’s foremost beauty spots and a site of special scientific interest (SSSI) and would take generations to restore.

It says efforts to reach an agreement with the quango on restoration work have been rebuffed.

Lawyers for the estate gave the SNH a deadline of the end of last week to reach a settlement, or they will launch legal action for damages.

They are demanding that the quango covers the cost of felling dead trees that are still standing, removing felled timber to the mainland, lost timber value and management and legal costs, totalling £152,340. They are also insisting that SNH makes a public apology.

Simon Miller, Luss Estates chief executive, said: "It beggars belief that the body that is supposedly responsible for protecting our natural heritage left Inchtavannach looking like a wasteland.

‘This is a tragedy that cannot be undone for generations. To make matters worse, after behaving so recklessly and admitting they did not appreciate the impact their work would have, Scottish Natural Heritage has dragged its feet for years when asked to do the bare minimum to start to put matters right.

In a statement, the estates say freedom of information requests have now uncovered correspondence which makes clear that the poisoning of the trees by Scottish Natural Heritage was unauthorised and that a felling licence was required.

The correspondence also suggests that the chemical glyphosate was used to kill the trees.

In many parts of the world glyphosate is banned, and in the US it has recently been the subject of a legal case against Monsanto involving a terminally ill cancer patient.

Scottish Natural Heritage told the Reporter that Inchtavannach is internationally important for its oak woodland but the condition of the woodland has been affected by a lack of regeneration, a lack of dead wood and the spread of non-native plants.

It added: "We have worked with Luss Estates and the tenant over several years on agreed management measures to improve the condition of the woodland.

“We are disappointed to have received this claim as our staff continue to work closely with Luss Estates to find workable solutions to tackling the problems with non-native trees on Inchtavannach.

"We have asked our solicitors to respond to the letter, and it would be inappropriate for us to comment further at this time.”

Inchtavannach Island, which lies within Loch Lomond and the Trossachs National Park, has a number of relevant designations and recognitions.

It is a Site of Special Scientific Interest and a Special Area of Conservation.