Plans to build a solar energy park capable of supplying up to 9,000 homes have been opposed by the local authority.
An email sent by Blaenau Gwent County Borough Council to the Welsh government says the development would have an "unacceptable" impact on an "undisturbed" rural landscape.
The farm would be set within the 143-acre Wauntysswg Farm near Tredegar.
The Welsh government has the final say on planning approval.
The formal objection notes the site's "pleasant views" into the Rhymney Valley and argues that a development of such scale would transform "historical farmland characteristics to one of an industrial renewable energy plant".
The application has been submitted by Elgin Energy, which operates solar farms across the UK.
The company declined to comment.
Blaenau Gwent council says it supports the national drive towards renewable energy, and has approved several wind turbines and a 14 megawatt solar farm elsewhere in the county borough.
A report also notes a short-term positive benefit of local employment opportunities during the estimated four-month construction period.
But principal planning officer Justin Waite, writing to the Planning Inspectorate, said: "It is, however, essential that as we go forward and consider new renewable energy developments, we ensure that the right developments are delivered in the right locations without unacceptable impacts on the local area."
"Unfortunately, the council is of the view that the proposed solar park at Wauntysswg Farm does not meet this essential requirement."
Concerns have also been raised about the impact on the nearby Tredegar Ironworks Cholera Cemetery, a monument of national importance recognising the local people who died of the epidemic in the 19th Century.
Cadw, the government body responsible for historic monuments in Wales, say the scheme would have an "unacceptable adverse impact" on the cemetery's setting.