Proposals for a nuclear power station on the Suffolk coast could be put at risk if local calls for investment are ignored, a council planner has warned.
Guy McGregor, the county council's cabinet member for planning, supports the plan to build Sizewell C next to an existing plant near Leiston.
But formal funding proposals for a bypass and other infrastructure is needed, he said.
EDF Energy said local people were still being consulted on the plans.
Councillors are being recommended in a report to support the plan at a cabinet committee meeting on 29 January because of the jobs and long term business opportunities it is expected to create.
But the report also criticises EDF Energy for providing "inadequate information" on plans for an A12 bypass around Little Glemham, Marlesford, Stratford St Andrew and Farnham and on developing the local economy.
It also calls for greater transparency and investment in transport infrastructure from EDF Energy.
Mr McGregor, the cabinet member for planning, said: "EDF is at risk of snatching defeat from the jaws of victory if it doesn't listen to calls for investment in infrastructure and community facilities.
"The energy company must take due note of the views being expressed.
"We support the development of Sizewell C and we want to do right by the country in terms of its long term energy needs.
"But we also want to make sure Sizewell does right by Suffolk and doesn't leave the county short changed from this significant development."
Andy Smith, Suffolk Coastal District Council's deputy leader and cabinet member for planning, said: "While we support the project in principle, its scale is huge, both as a construction project and then for the foreseeable future.
"Our job is to maximise the advantages and minimise the problems which it will bring to our area,."
Both councils are calling on EDF Energy to:
•Fund essential rail, road and sea transport - especially an A12 bypass.
•Create jobs and business opportunities for local people, both during construction and in the long term.
•Limit impact on the county's tourism industry and outstanding natural beauty.
•Fund community benefits such as sports pitches, community halls and improved access to the countryside.
•Ensure that there is the right housing in the right places for workers on the project.
When asked about the concerns EDF Energy said in a statement: "Since EDF Energy launched the Stage 1 Consultation for Sizewell C on 21 November we have seen over 3,000 local people at several exhibitions and events.
"We have welcomed the range of questions on areas as diverse as employment opportunities through to our transport strategy for the project.
"What is clear is that we remain as committed as ever to maximising the benefits a new nuclear power station would bring to Suffolk whilst minimising the impact.
"It is important to stress that people can still have their say on the Sizewell C Initial Proposals as the consultation continues until 6 February."