Community leaders are set to withhold their backing for a £14billion new nuclear power plant on the Suffolk coast – saying EDF Energy needs to do a lot more work to reassure the public.

Senior councillors and officials are voicing “deep concerns” over some aspects of the latest consultation and how the impacts of the massive development will be mitigated.

While they support the principal of a new power station and recognise the benefits for the local economy, they say there is a “lack of information” still – four years since the last consultation – on a range of vital issues, including traffic and transport, the environment, and design of the plant.

They say it is unclear how social and economic benefits will be delivered to communities, and some areas of concern have not been covered at all.

Both Suffolk County Council and Suffolk Coastal District Council have been frustrated by the short period of the Stage 2 consultation, which they say made it challenging for the councils to coordinate their response.

They are urging EDF to allow significantly more time for the Stage 3 consultation, the final stage, given the large amount of material expected to be released at that point.

Suffolk County councillor Guy McGregor, chairman of Sizewell C Joint Local Authorities Group (JLAG) said: “Whilst we understand the need to address the UK’s future power needs and we broadly support the principal of a new nuclear power station being built in our community in Suffolk, we are not able to support the specific proposals put forward at this time.

“We believe that the impacts of the development planned in its current guise are as yet, not fully mitigated or evidenced.

“There is much more work for EDF Energy to do to convince us that their plans are up to the expectation we place upon them on behalf of the people of Suffolk. For a number of reasons outlined in our report, we are not yet fully convinced that the benefits of EDF’s proposals outweigh the impacts on the community.”

The authorities also want to see details of community benefits.

At Hinkley Point C, EDF is spending £92million on compensation and mitigation – just 0.6% of the total cost of the project – but as yet the benefits from Sizewell C have not been costed.

The council says: “Sizewell C is, in comparison with Hinkley Point, a much more complex site with more demanding mitigation requirements for its impacts on the AONB.”

Mr McGregor said: “Suffolk wants to do right by the country in respect of this project, but the country has to do right by Suffolk. When you consider the huge cost of the power station we are asking for very little.”

The councils are keen to collaborate with EDF to help them develop their proposals.

Suffolk Coastal councillor Geoff Holdcroft, vice chairman of JLAG, said the district council had particular reservations over a number of aspects and wanted absolute clarity from EDF Energy before it was prepared to offer support.

He said: “We do recognise the positive social and economic benefits that may come to local communities in East Suffolk but we need to know more about how these benefits will be achieved and this can only happen if we work with EDF Energy and Government to make sure our voice is heard. We want EDF Energy to put more effort into addressing the concerns that have come directly from our communities and from our local authorities.

“This massive project can be good for Suffolk, but we need much greater detail and evidence from EDF Energy before we are able to offer firm support.”

EDF has said that it wants to hear all views on its proposals and will take these into account as it prepares for Stage 3 consultation. The current consultation ends on February 3.

EDF Energy’s latest Sizewell C consultation comes in for hard-hitting criticism from the two councils over failings in the way it addresses the impact the gigantic project would have on Suffolk’s nationally-acclaimed coast and heaths landscape and the area’s sensitive ecology, writes environment correspondent John Grant.

Serious concerns are raised by Suffolk County and Suffolk Coastal District councils over the effects the huge scheme would have on the Suffolk Coast & Heaths Area of Outstanding Natural Beauty (AONB), the economically important tourism that the designated beauty attracts and the area’s internationally acknowledged natural habitats and rare and protected wildlife.

The councils describe the Stage 2 Consultation document as “disappointing in that it fails to recognise or truly acknowledge the environmental challenge that development at this site faces, nor the likelihood of residual impacts in a number of areas”.

They say: “Some environmental issues are hardly covered at all, for example – some ecological surveys appear to have been overlooked. There needs to be further significant work to seek to survey, understand, quantify and qualify these impacts.”

They were “not satisfied” that the consultation “adequately recognises the status of, or the likely impacts of the proposal on, this nationally designated landscape.”

They remained “deeply concerned about design of the main reactor site, given that Sizewell C will be sited in a landscape of national and international importance and sensitivity, given its location within an AONB and on a designated Heritage Coast.”

Sizewell C’s design “should be an environmental exemplar” and improvement was expected. Where this was not possible there a “compensation package due to the lasting impact on and damage to the AONB” was expected.

Among a wide range of other environmental concerns, the councils say the area of the Sizewell Marshes Site of Special Scientific Interest (SSSI) expected to be permanently lost had increased from 4.6 hectares in Stage 1 to 5.55ha, and some habitat now proposed to be lost was “much harder to replace” elsewhere.

Campaigners have voiced “huge disappointment” that the county and district councils are not pressing for a new road to directly link the A12 and Sizewell.

Traffic along the B1122 is forecast to rise by 542% during the peak construction period – and residents in Yoxford, Theberton and Middleton are worried at the congestion, pollution and danger this will cause.

County councillors Michael Gower and Richard Smith are both concerned that a suggested link road, called the D2, has not been put forward by the councils.

Mr Smith said: “This road has been costed at £40m – it’s not a showstopper. It would be a quicker and safer route to and from the site and would provide a lasting legacy for this part of east Suffolk.”

Mr Gower said: “The cost is a tiny percentage of the £14bn it will cost to build this power station, and it will provide a much better route to and from the growing town of Leiston and be a positive legacy.”

The councils’ joint response will criticise suggested improvements, including a roundabout or traffic lights at the Yoxford A12 junction, because not enough evidence has been provided to show it would be a solution.

JLAG chairman Guy McGregor said it was up to EDF to bring forward options.

Meanwhile, providing a bypass for two villages – Farnham and Stratford St Andrew – should be the “absolute bare minimum” that EDF should provide, according to the councils.

They are hoping the company will give more to the Suffolk Energy Gateway project and say road improvements, including a Four Village Bypass to include Little Glemham and Marlesford, should be ready ahead of the development.

However, the commitment to bypass two communities should give the councils leverage to persuade Government to add funds.