Plans to develop a nuclear power station "do not go far enough" to address the impact on a local community, a council has warned.
Plans for the Sizewell C plant on the Suffolk coast have been put forward by EDF Energy.
But Conservative-run Suffolk County Council stressed it could not back the plans in their current guise, the Local Democracy Reporting Service said.
A council spokesman said the authority "must not give EDF a blank cheque".
On Monday, the cabinet of East Suffolk Council - also Conservative-controlled - had unanimously agreed to take "a neutral approach... neither fully supportive nor against the proposals".
But while the county council's cabinet said it supported the principle of the development, it also used Tuesday's cabinet meeting to call on EDF Energy to "focus on doing something about Suffolk's very reasonable concerns".
Councillors said these included the impact on fish habitats and other wildlife, the potential detriment to the tourism business - and increased freight on the A12.
The county council's cabinet member for environment and public protection, Richard Rout, accused EDF Energy of "not listening to Suffolk and its communities".
"The issue is not a lack of in-principle support from Suffolk County Council... [EDF] simply does not appropriately and sensitively address the impacts on our communities and the environment," he said.
"We must not give EDF a blank cheque in delivering their development in a way that does unnecessary harm to our county."
He acknowledged the benefits it would bring - including an estimated 1,500 apprenticeship roles, additional jobs and the knock-on boost to the local economy.
Elfrede Brambley-Crawshaw, leader of the county council's Liberal Democrat, Green and independent group, said: "We are very pleased Suffolk County Council have taken a more robust view than East Suffolk, and we also support the view that EDF have not mitigated the impact of Sizewell C."