Southern Water has been fined a record £90m at a court in Kent after admitting to deliberately dumping billions of litres of raw sewage into protected coastal waters over many years. 

Mr Justice Jeremy Johnson, who was sentencing the privatised water company at Canterbury Crown Court on Friday, said that the organisation had discharged between 16bn and 21bn litres of raw sewage into coastal areas including Herne Bay and Whitstable. 

Southern Water admitted to 6,971 illegal spills from 17 different locations in Hampshire, Kent and West Sussex between 2010 and 2015.

"These offences show a shocking and wholesale disregard for the environment, for precious and delicate ecosystems and coastlines, for human health, and for fisheries and other legitimate businesses that operate in the coastal waters," Mr Justice Johnson said. 

He added that the sewage discharges were the result of "negligence" and noted that the company had a history of criminal activity for its "previous and persistent pollution of the environment". 

Southern Water had 168 previous offences and cautions which had been ignored. "There is no evidence the company took any notice of the penalties imposed or the remarks of the court. Its offending simply continued," he said. 

The prosecution came about as a result of a five-year investigation by the Environment Agency, launched following the deterioration of oyster beds and shellfish flesh and high levels of faecal bacterial contamination found in the coastal waters.

The investigation, known as "Operation Garden", uncovered "very serious widespread criminality" by the company over a period of nearly six years, which was known about at the highest level. 

The court heard that Southern Water employees locked documents away and tried to stop regulator’s officers inspecting sites in an "unprecedented" effort to hinder the Environment Agency’s investigation