A court decision has annulled all rights given to Shell to explore oil and gas using seismic waves on the Indian ocean, off the coast of South Africa.

The High Court in the Eastern Cape town of Makhanda backed a suit filed by conservationists and local groups who shared concerns on the environmental consequences of Shell’s project.

Members of the court declared Shell was banned from “undertaking seismic survey operations”, a decision that had an immediate effect.

Shell had planned to start exploration over more than 6,000 square kilometres (2,300 square miles) of ocean off South Africa’s Wild Coast — a 300-kilometre (185-mile) stretch. The ecologically sensitive area known as the Wild Coast is dotted with a marine stretch that is home to nature reserves.

The surveying technique entails using seismic blasts that bounce shockwaves off the sea bed. The return signal is turned into a 3D model to highlight locations with energy-bearing potential.

But the Anglo-Dutch giant ran into fierce opposition, as campaigners warned of potential harm to whales, dolphins and seals, which rely on hearing to survive, as well as to birds, fish stocks and microscopic plankton.

In his concluding remarks, the judge said consultations with coastal communities had been “substantially flawed”, which made Shell’s survey application “unlawful and invalid”, a valid reason to nullify Shell’s previous rights.

A Shell spokesperson said: “We respect the court’s decision and have paused the survey while we review the judgment.”

They did not say whether the corporation would file an appeal but reiterated that the operation was safe.

“Surveys of this nature have been conducted for over 50 years with more than 15 years of extensive peer-reviewed scientific research.”

The company’s area of interest is in the ocean floor 20 kilometres (12 miles) off the coast, in waters 700 to 3,000 meters deep (2,300 to 10,000 feet).

Exploration had been scheduled to start on December 1 and last up to five months.