The United Nations has accused the UK Government of suspicious actions over plans to develop its first nuclear power station in a generation.
Environmental inspectors have warned there are concerns about a lack of talks with neighbouring countries, including Ireland, over potential risks posed by the Hinkley Point C plant on the Bristol Channel.
The nuclear facility could supply 5% of the UK's energy needs and would be 150 miles from the Irish coast if built.
A special UN environmental committee has written to the Government warning that it failed to notify countries which could potentially be affected by fallout or pollution from Hinkley, regardless of how unlikely an accident is.
"The committee found that there was a profound suspicion of non-compliance," the UN states.
Vesna Kolar Planinsic, chair of the implementation committee on the Convention on Environmental Impact Assessment in a Transboundary Context, said UK representatives will be called before a hearing in December to explain their actions.
The committee said concerns have been raised over Hinkley by the Netherlands, Belgium, Spain and Norway.
It found that, bar "informal exchanges" with the Irish Government and contacts with Austria following an official approach, Britain did not inform other neighbouring states of its plans.
The UN said some countries maintained they could not exclude the significant adverse environmental impact of the proposed activity on their territory. Under UN and European rules, neighbouring countries must be contacted unless such risks can be ruled out.
Britain plans to have the first nuclear reactor at the Hinkley Point C site churning out power in 2023.
The Somerset plant is part of a multibillion-pound plan to replace ageing, inefficient and polluting power stations in Britain over the coming decades and ensure security of energy supply.
It is backed by billions in subsidies over 35 years from the British taxpayer to guarantee power prices from the plant and investors include France's EDF and Areva, and Chinese state-owned CGN and CNNC.
The European Commission is investigating whether support for nuclear complies with state aid rules.
The national trust, An Taisce, lost a judicial review in the UK courts last year over the Hinkley plan and is planning to seek an appeal next week.
The UN letter to the UK's Department for Communities and Local Government is expected to lend weight to the argument for a hearing in the Court of Appeal.