Satisfaction with Southern Rail has plummeted in the latest Which? customer satisfaction survey, but the consumer group said the whole sector is failing passengers.
Southern achieved an overall score of 21%, with one star ratings for punctuality, reliability, seat availability, frequency and value for money.
Southern and Southeastern services run from Victoria
Its overall rating has fallen by over a half, from 44% a year ago.
Almost half (46%) of Southern customers surveyed this time reported that their last journey was delayed.
After a survey of over 2,000 commuters, Which? has launched a campaign ‘taking the industry to task on unacceptable services that don’t deliver even the basics for long suffering passengers’.
It called for train companies to respect passenger rights and comply with the law; the regulator to be given ‘real teeth’ to hold the rail industry to account; and the Government to ‘swiftly bring forward reforms that put passengers first’.
Vickie Sheriff, the Which? director of campaigns and communications, said: 'After months of disruption, it’s no surprise to see Southern at the bottom of our customer satisfaction survey.
'Though Southern have performed particularly badly this year, the whole sector is continually failing passengers.'
Thameslink and Great Northern – also within the GTR franchise that includes Southern – came third from bottom in the survey with 32%, scoring one star for frequency and the condition of their carriages.
Southeastern was second from bottom with a rating of just 31% and one star for seat availability.
The re-letting of the South Eastern franchise, currently held by Southeastern, is at the centre of a devolution row between London mayor Sadiq Khan and transport secretary Chris Grayling.
Merseyrail came top in the survey with a customer score of 72% and five star ratings for reliability and frequency, while Virgin Trains West Coast came second with a five star rating for reliability.
The Rail Delivery Group, representing train operators, questioned the relatively small sample size of the survey.
Jacqueline Starr, managing director customer experience, said train operators know they must do better but added: 'It is not true that the whole railway is failing passengers.'