It comes as the utilities firm admitted 51 criminal charges brought by the Environment Agency after its investigators examined 17 treatment works.
The environmental impact was ‘immense’ but cannot be fully measured, Canterbury Crown Court has been told today.
Sewage released in the discharges ‘contains all sorts of waste including human pathogens and plastics’ causing harm to coastal waters and contaminates shellfish.
Portsmouth Traffic: M27 between junctions 11 and 12 closed throughout August amid footbridge repairs with A27 diversion in place
‘I watched ten years of my children’s lives go up in flames': 'Traumatised' Paulsgrove mum of five launches fundraiser to find family new home after they 'lost everything' in bedroom fire
Police update over alleged violent gang rape of woman at address in Portsmouth
Thunderstorms in Portsmouth yellow weather warning: The Met Office forecast for the next three days in city, Fareham, Gosport, Havant and Waterlooville and Hampshire
Hayling Island's beloved kitesurfing festival cancelled after council bailout is refused
The charges include 674 discharges lasting 4,938 hours in duration at Budds Farm Waste Water Treatment Works in Langstone Harbour.
Those discharges took place between January 2010 and December 2015.
Between April 2010 and December 2012 there were 49 discharges totalling 335 hours at Bosham, West Sussex, and 226 discharges totalling 9,890 hours at Chichester.
Across all 51 charges admitted by Southern Water there were 6,971 discharges lasting 2,571 days – or 7.04 years – in total.
The Environment Agency’s barrister said the firm ‘prioritised its finances above environmental compliance’ and ‘deliberately avoided’ the causes of the spills.
Andrew Marshall, prosecuting, said: ‘All could have been avoided since the causes were known but deliberately avoided by the defendant company.
‘However, there was a general unwillingness by the company, despite knowledge of its failed systems, to fund the necessary staff, maintenance and upgrades that would make the company compliant.’
Mr Marshall added: 'This is an exceptional case that brings together thousands of separate matters (each of which would amount to an offence) under the umbrella of a 51 count indictment and addresses a wide geographical area, multiple sites and offending over almost six years.'
Southern Water runs around 365 wastewater treatment sites across Kent, Sussex and Hampshire.
Environment Agency investigators found wrongdoing at 17 sites over the period of January 2010 to December 2015.
Mr Marshall said the firm had been convicted of offences every year between 1999 and 2016.
‘The company’s many previous convictions - convictions spread over many years and in relation to many different sites - place the board and senior management on the clearest possible notice as to the company’s failings and offending,’ he said.
He added: ‘An overview of those convictions shows they directly arise from failing equipment, poor maintenance of equipment and alarms, and an inability properly to respond to issues as they arise.’
The company had a £213m operating profit in the year to March 2020, accounts show.
The sentencing hearing against Southern Water started today before the judge, Mr Justice Adam Johnson, and is expected to conclude on Friday.