LEADING seismologists and geologists have called for an immediate moratorium on oil drilling in Surrey after a dozen earthquakes shook the county in the last four months.

Experts in the hydrocarbon industry wrote to the Times yesterday, as well as to Business Secretary Greg Clark and the heads of the oil industry regulators, to warn that “public health and the environment are not being adequately protected given the unstable geology.”

They added that this instability “had not been identified before planning permission and other permits were issued for the currently active drill sites.”

The British Geological Survey is investigating 12 earthquakes in the area since April 1, which occurred at depths between 400 metres and one kilometre, by installing five seismic monitors to calculate more precisely the depth, location and cause of the quakes.

But the four leading petroleum geologists said that activities at oil drilling sites in Horse Hill and Brockham — the subject of long-running, locally led protests — might be causing the quakes, which may have damaged the well casings and made them unsafe.

Professor Richard Selley of Imperial College London said: "The location of the swarm close to two active fields suggests more than serendipity and merits investigation.”

Professor Stuart Haszeldine of the University of Edinburgh school of geosciences added: “These earthquakes are unique and unprecedented events in the region and seem to be increasing.

“This activity needs to be paused immediately to understand what these companies are doing underground.”

Surrey County Council is due to consider an application for a three-year oil exploration licence for Brockham next week.