A secret counter-terrorism review of Britain's nuclear power plants is under way after fears arose over safety at the giant Sellafield reprocessing site.
Officials at HM Inspectorate of Constabulary, which is responsible for assessing the work of police forces across England, Wales and Northern Ireland, have begun an urgent assessment.
It is understood their work will cover the protection of pipelines, oil refineries and other key parts of national infrastructure but will focus on Sellafield.
The Cumbria site includes a £120 million bunker that will eventually store 100 tonnes of raw plutonium as well as redundant facilities built as part of early nuclear defence work.
Concerns about protecting the plant may have come to light during an exercise in which special forces posed as terrorists to test security, according to The Times newspaper.
Officers at Scotland Yard's Counter Terrorism Command and MI5, which operates the Centre for the Protection of National Infrastructure, have been kept up to date on the progress of the review.
The ongoing review will be discussed during a meeting between officials at the Department of Energy and Climate Change (DECC) and members of the Civil Nuclear Constabulary Authority today.
They include retired police chief and former Association of Chief Police Officers chairman Sir Chris Fox, who now leads the authority, and Tony Regan, its executive director.
The Civil Nuclear Constabulary, which has a force of about 800 officers, most of whom are trained marksmen, is unusual because it answers to DECC and not the Home Office.
The force's main role is protecting the country's nuclear estate from the threat of international terrorism and has recently upgraded the quality and type of weapons and ammunition used by staff.
A DECC spokesman said: "Security arrangements are kept under constant review as part of a continuous process to ensure existing arrangements are robust and effective.
"We do not comment on the detail of operational security matters at civil nuclear sites."
No one was available at the Civil Nuclear Constabulary or the Civil Nuclear Constabulary Authority to comment.Reuse content