A leading group of conservationists has gone to the Court of Session in a fresh attempt to halt a 67-turbine windfarm which could be built in a Highland mountain range.

The John Muir Trust, which works to protect wild land in Scotland, wanted a judicial review of Highland Council's planning committee's decision to raise no objection to the development at Stronelairg, which sits in the Monadhliath Mountains.

Its claims that councillors, in refusing to block the renewables development, went against advice that the windfarm - spread over an area of 35 square kilometres, one and half times the size of Inverness - would destroy the character of one of Scotland's key areas of wild land.

The plans for Stronelairg, which have been submitted by SSE, formed the largest application of its type to be handled by Highland Council.

Planning chiefs advised councillors that the impact of the windfarm on wild land had been overstated by Scottish Natural Heritage and that it would not warrant an objection.

As a result, councillors voted not to object to the proposals as long as the original plans for 83 wind turbines were scaled back.

The John Muir Trust claimed it had received legal advice that the Stronelairg decision, taken by the south committee, was based on a fundamental misinterpretation by the council planning officials of the National Planning Framework, Scottish Planning Policy and the Highland-wide Local Development Plan - and was therefore unlawful.

John Hutchison chair of the John Muir Trust and resident within the council area, said: "This legal action is not directed against the councillors, who have to deal with multiple issues and are forced to rely on expert advice from officials."

Mr Hutchison said the conservation trust disagreed with the professional advice. He added it was "fundamentally in conflict with the existing local and national planning policy - which states explicitly that authorities should safeguard the character of wild land areas." He added: "Since the decision was taken, the Scottish Government has confirmed the existing protection of wild land and proposed a further strengthening of wild land protection.

"In the light of existing and emerging planning policy frameworks, the decision to not object to the Stronelairg application was, in our opinion, both unreasonable and unlawful."

Helen McDade, the Trust's head of policy, said the north planning committee recently raised objections to smaller developments at Glenmorie and Dalnessie on wild land grounds.

She added: "The council has not explained this fundamental inconsistency. However, it would be perverse if the very much larger Stronelairg proposal was not subject to the same rigorous public scrutiny."

The application will be considered by Scottish Ministers after councillors voted 11 to three in favour of raising no objection if the windfarmwas reduced in size and met other conditions.

SSE have been gathering wind data from the site since 2009 with a decision due on the plans later this year. If approved, the energy firm expect it will take three years to build.

Stronelairg has been marked as a wild land area in Highland Council policy and is due to form part of a wider "core area" of such landscapes.

First Minister Alex Salmond recently urged Scottish Natural Heritage to draw up such zones in a bid to give planners a clear guide when it comes to deciding on planning applicaitons.

Under the move, around 28% of the countryside will be designated as wild land that should not be built on, apart from in exceptional circumstances.

A spokesman for SSE said: "We note the recent activity from the John Muir Trust in relation to Stronelairg wind farm with disappointment. Stronelairg is a sensitively designed wind farm based around existing hydro infrastructure which would bring significant economic benefits to the local economy."

Highland Council was unavailable for comment.