The Bronte Society has objected to a test mast bid for a multi-million pound windfarm as developers revealed a new site map larger than the original plans.

Banks Renewables is looking to spend about £12.5 million building up to four turbines on moorland south of Denholme, near Thornton.

A 60m-high test mast will be put up to collect wind data if a planning application is granted ahead of a full application to Bradford Council, expected to be submitted in April.

The society has describing the temporary structure as “further pollution of the skyline”.

In a letter of objection to Bradford Council, chairman Sally Macdonald said: “The Bronte Society cannot support the erection of any structure which, even if of a temporary nature, has implications for the future permanent defacement of the views from Haworth moorlands. Haworth and its moorlands have international cultural and historical significance and any proposals which have an adverse impact on this significance are to be disapproved of.”

Critics from Thornton Moor Wind Farm Action Group say an original map published by Banks showed a smaller site, away from homes in Denholme. But its latest draft “scoping” report – submitted to the Council as part of its application to put up the test mast – shows an extended boundary near homes in Denholme Gate.

A spokesman for Banks said the new map was a “study area”, which shows where environmental impact assessments had been carried out.

However, Anthea Orchard, who set up the action group in 2010 to oppose the plans, said: “The wind farm could end up being closer to houses in Denholme.

“It is an extended boundary from what they publicised originally without consultation and, whilst we realise this is only a scoping report for research and not part of an application for the wind farm, it could pave the way for turbines to be put up closer to homes.”

Mrs Orchard said the group also had concerns about the loss of green fields, the site’s close proximity to geological and biodiversity areas such as the South Pennine Moors Site of Special Scientific Interest and the visual impact on the area.

She said there had also been a “lack of good quality information” provided in the latest application about where the wind test mast would be situated.

Mark Dowdall, environment and community director for Banks, said: “The 36-page scoping report that we recently submitted to Bradford Council sets out a detailed framework for the assessment of the development, and contains a great deal of information about every aspect of it.

“The area referenced in it is not the proposed turbine development area, but is in fact the ‘study area boundary’, which defines the land across which we have undertaken the Environmental Impact Assessment surveys.

“We’ve had a great deal of positive feedback about our Thornton Moor proposals from many local people over the last few months, and will continue to keep everyone fully up-to-date as we move towards finalising our planning application.”