A Scottish Government decision to allow more houses to be built on a woodland in the Cairngorm National Park is flawed and should be revoked, say environmental groups.

An expert report commissioned by a coalition of leading Scottish environmental organisations has concluded that a highly unusual directive giving the go-ahead for building issued by government planning chief, John McNairney, to the Cairngorm National Park Authority is "unreasonable", "incorrect" and "wrong" - and should be withdrawn.

McNairney ordered the park authority last month to reverse a previous decision not to zone woodland at Carrbridge for housing in its local development plan. This could mean that the land available for new homes in the village will double, increasing the number of dwellings from 36 to 72 or maybe more.

Now nine wildlife and countryside groups have written to McNairney. "The direction and the whole basis for it is wrong," they say. "The direction is therefore flawed and should be withdrawn."

This is the latest stage in a fierce and long-running battle over housing developments in the Cairngorms park. Local politicians argue that affordable new homes are needed, while conservationists say that precious wildlife sites must be protected.

"The park authority and two sets of government reporters have unanimously recognised that this woodland should not be allocated for development," said Gus Jones, the convener of the Badenoch and Strathspey Conservation Group. "The direction provides no reason why the local plan in the Cairngorms National Park should be hijacked."

Carol Evans, director of the Woodland Trust Scotland said: "The Scottish Government's latest demand that a large area of woodland that was previously safeguarded from development be earmarked for development is unreasonable."

Ancient woodland was an irreplaceable habitat developed over hundreds of years to support a rich variety of rare wildlife, she argued. "Any further loss is unacceptable, particularly within our national parks where the protection of natural heritage should be of paramount importance."

She was backed by Helen Todd, from Ramblers Scotland, who described native woodlands like those around Carrbridge as "fantastic opportunities for recreation". It was important to protect such areas from "inappropriate development which would destroy their special qualities", she said.

The Royal Society for the Protection of Birds (RSPB) criticised the Scottish Government for failing to justify its demand for more development in the Cairngorms. "Scottish Ministers need to provide a transparent explanation of how the environmental implications of this decision were reached if confidence in their environmental credentials is not to be damaged," said head of planning at RSPB Scotland, Aedán Smith.

According to the Scottish Government, a "factual error" had been made, wrongly suggesting that there were no live planning permissions in place for Carrbridge. This was what had prompted ministers to issue a direction to the park authority.

"We have received a letter from the Badenoch and Strathspey Conservation Group requesting the direction to the Cairngorms local development plan be withdrawn," said a government spokesman. "We will consider the points raised and respond in due course."

Murray Ferguson, director of planning at the Cairngorm National Park Authority, pointed out that ministers had exercised their right to modify the local development plan. "This is a relatively small change, but of great significance to Carrbridge," he said.

"The other policies in the plan have not been changed and many of these will be relevant when it comes to considering any development proposal on the site. The next step for us is to take the plan to our board for consideration at the end of March."