Mitigating proposals for the proposed Sizewell C nuclear power plant were "a disappointment", a government Planning Inspectorate hearing was told.
Suffolk County Council told the four-day public hearing that it could not support the project as it stood.
The council said it needed reassurances on sea and rail transport options, and on how jobs and training could benefit local people.
The developer, EDF, has not responded yet to the comments made so far.
The electricity plant for the Suffolk coast would be built next to the existing Sizewell B reactor, and EDF said it would generate 3.2 gigawatts of electricity, enough to provide 7% of the UK's needs.
Some 15 voices spoke at the Tuesday morning session, almost all critical of either the power plant itself or EDF's mitigation impact proposals.
Speaking for Suffolk County Council, Richard Rout said that while it supported the project in principle, "the development as it stands was currently a disappointment for many who may wish to support it".
EDF Energy estimated Sizewell C would create 5,000-8,000 local jobs during construction, which could take about nine years and cost £20bn.
The company has also proposed to transport a large proportion of construction materials by sea and rail, amid fears local roads would not be able to cope with the increase in lorries.
Mr Rout said "we want the reassurance that all transport proposals are deliverable" and called for caps to ensure these are "delivered in a timely manner".
Despite having several reservations about the project, including noise and ecology issues, East Suffolk Council said its position on Sizewell C remained "neutral".
Spokesman Craig Rivett cited the benefits to jobs and skills locally, providing local businesses were "allowed to enter and benefit the supply chain".
He called for a "tourism fund" to help mitigate any adverse impact construction would have on the tourism sector.
Birdwatcher, Alan Hatt, who moved to Suffolk 13 years ago, claimed the reactors would be "obsolete by completion".
He feared natural habitats on the coast, which is an area of outstanding natural beauty, would be affected by "light, noise and dust" from construction.
The hearing, being held online, continues until Friday afternoon.
The government will have the final say on whether the plant can be built.