Questions about UK scrutiny of Chinese nuclear tie-up
The government is refusing to say whether it has followed its own rules in allowing China's investment in the new £24bn Hinkley nuclear power plant, citing questions of national security.
Chinese involvement in UK energy schemes remains controversial, not least because of the historical links between its industry and the military.
The National Security Council is supposed to review critical projects.
But ministers have consistently refused to say whether this has been the case.
The BBC requested information, under Freedom of Information laws, about whether the National Security Council had discussed China's investment in a proposed new Hinkley C reactor as part of a consortium led by French firm EDF and if it had, whether it had been approved.
In a delayed response, the government confirmed the information was held by the Cabinet Office but refused to say whether the NSC had approved or even discussed China's expected 30-40% stake in the Somerset project or the implications of its long-term aim of building nuclear reactors of its own in the UK.
In his response, Cabinet Office official Roger Smethurst, told the BBC: "There is a general public interest in disclosure of information and I recognise that openness in government may increase public trust in and engagement with the government. There is a definite public interest in members of the public being able to understand decisions taken on investment in critical national infrastructure."
But he added: "I have weighed these public interests against a very strong public interest in safeguarding national security."
National security considerations could only be overridden in exceptional circumstances, he said, adding that "the balance of the public interest favours withholding this information".
But Derek Smith, head of communications for the National Security Council (NSC), told the BBC that foreign investment in critical national infrastructure projects like Hinkley C fell under the aegis of the body, established by David Cameron in 2010.
"The government has put in place an approach which enables it to assess the risks associated with foreign investment and develop strategies to manage them," he said.
"The NSC brings together the economic and security arms of the government and is the forum that ultimately balances the risks and opportunities of inward investment decisions" he said in answer to questions.
The Cabinet Office said Chinese companies had "strong credentials and an established track record in delivering safe nuclear power over the past thirty years" and any company involved in the UK's nuclear power industry does so in accordance with the most stringent regulations in the world.
The Labour MP Dr Alan Whitehead, a member of the Energy and Climate Change Committee, said the government's refusal to say whether it had followed its own rules was "not acceptable".
"There is clearly an issue of national security about a Chinese government stake in and possible control of the building and operation of a British nuclear power plant," he said.
"Refusing to discuss it by hiding behind supposed national security will cause most people to conclude that expediency is trumping security in the review process."
Antony Froggatt, senior research fellow on energy and environment at the Chatham House think tank, said openness about the Hinkley project was "absolutely vital" given the scale of state financial support.
"The government should therefore make public the details of the discussions in the National Security Council and other key decisions such as within the HM Treasury on the UK Guarantee Scheme to inform the public and the wider EU about the cost, security and overall value of the project," he said.
French firm EDF had been due to make a final investment decision in Hinkley C by the end of last year but the project is still in the balance, not least because of the debts weighing down the French reactor developer Areva.
Similar reactor projects in France and Finland are running hugely over budget and behind schedule.
Meanwhile China is poised to increase its influence in the UK energy market with reports that the state owned China General Nuclear Corporation was preparing to pay an estimated £100m for an 80% stake in three UK wind farms which would be Beijing's first purchase of onshore wind generation capacity in the west.