THE bitter and twisted arguments over how to manage the monarch of the glen have taken a dramatic new turn, with Scotland's most august environmental organisation accused of betraying the environment.

The National Trust for Scotland (NTS) has come under fierce fire from fellow conservationists for bowing to pressure from landowners – including the Queen's estate at Balmoral – to reverse plans to cull thousands of red deer in the Cairngorms.

Populations of the deer in parts of the Highlands have trebled since the 1950s (see table right). This is partly because they have been encouraged and fed by sporting estates to ensure that there are plenty of stags to be shot by paying visitors.

But burgeoning numbers of the beasts have ravaged the natural environment, eating saplings and heather, degrading the landscape and stunting the growth of forests.

As a result the future of red deer has become the most heated – and paradoxical – of Highland disputes. Environmentalists want to cull large numbers of them so that ancient woodlands can recover, while landowners want to protect them so they can be killed for sport.

The latest flashpoint is at Mar Lodge, a famed mountain estate near Braemar, which was taken over by NTS in 1995. Because of complaints from neighbouring landowners, including Balmoral, it conducted an independent review of deer management which reported last year.

The NTS chairman, Sir Kenneth Calman, said recently that the Trust had made "one or two mistakes" and had culled too many red deer in the last 15 years. Numbers on the estate are said to have fallen from 3500 to 1600.

He argued that there was no need to cull many more deer. "We've learned a significant number of lessons from what's happened in Mar Lodge," he told BBC Countryfile. "These lessons, I think, can be translated across the country, and in that learning process we can reduce the culls to a minimum."

Calman's remarks have upset environmentalists, with one leading expert demanding his dismissal. "Calman's weak, unscientific attitudes have undermined the NTS staff for no good reason other than caving in to irrational and misguided political pressure," said Dr Adam Watson.

Watson, who will be 82 this month, is a renowned mountain ecologist and an internationally acknowledged authority on the Cairngorms. "This is scandalous," he told the Sunday Herald. "He should be sacked for bringing the NTS into disrepute."

Dave Morris, director of Ramblers Scotland, accused Calman of losing sight of environmental and recreational priorities. "He is touching his forelock to those influential landowners who see nothing wrong with overgrazing our moorlands and woodlands just so that there is always a big stag to point their rifle at," he said.

"The NTS needs to come to its senses, remember how much public money has supported its activities so far, and engage with outdoor recreation interests so that public confidence in what it is trying to do at Mar Lodge can be regained."

The NTS has also been criticised by Mike Daniels, a deer expert who lives on Mar Lodge estate. Protecting the environment was the "Cinderella" of deer management at the expense of the "ugly sisters" of economic and social development, he warned in the magazine, Wild Land News.

The NTS was defended, however, by the Association of Deer Management Groups, which represents landowners. The association agreed with much of what came out of the review of deer management, and was looking forward to working with the NTS to reach a "consensus view" on the way ahead.

"We need to get away from the polarised position where you can have trees or you can have deer but you can't have both," said the association's chairman, Richard Cooke. "You can have both but some give and take is required to agree what best meets all requirements."

David Frew, the manager of Mar Lodge Estate, insisted that NTS was continuing to protect the Caledonian pinewood in parts of the estate by culling red deer. "It's a policy we have applied consistently, neither abandoning nor significantly amending it," he said.

But Mar Lodge was also a sporting estate, and it limited the number of deer it shot "so that the numbers are there for future years", he added. "It's all about pursuing a balanced approach which harmonises conservation, field sports and public access objectives, rather than adhering to polarised doctrine."

Frew accepted that NTS could have done more to explain its approach. "We won't be making that mistake again," he said. "We're working to a 200-year timeline, and the past few years confirm we're making real progress."