Global green campaigner Greenpeace is threatening to take legal action against E.ON and other potential power operators for rushing ahead with plans to build new reactors in England before full permission had been given.

The move has been triggered by reports that drilling of preparatory bore holes for new reactors will start in August at Oldbury in Gloucestershire. EDF is said to be considering similar work, writes The Guardian.

A Greenpeace spokesman told the newspaper that its lawyers were reviewing a situation that made a mockery of a whole raft of hurdles that were meant to be overcome before the government starts official licensing for the sites in 2013.

The environmental campaigning group said there has not yet been a final national policy statement on nuclear, an official ‘justification’ process for building more stations as needed by law, or an assessment of reactor designs by the Nuclear Installations Inspectorate (NII), the newspaper reports.

E.ON denied that it was jumping the gun. “We will do nothing of a serious nature until the government gives the green light. This is just preparatory seismic work to make sure the ground is suitable. We are not preparing the foundations or anything like that,” a company spokesman told the newspaper.

Power giant EDF also said it is carrying out various studies at sites such as Hinkley Point in Somerset ahead of putting in a formal planning application next year.