The owners of Southern rail have been fined £13.4m for poor performance, the Department for Transport has announced.
The government said the fine on Govia Thameslink Railway (GTR) would have been higher, but most of the delays had not been Southern’s fault.
The DfT said strikes and unprecedented levels of sick leave were also to blame.
The RMT union was critical of the fine, saying the government had let Southern and its parent company off the hook.
Mick Cash, the general secretary of the RMT, said: “This pathetic response to the abject failure by Southern/GTR to deliver on their contract doesn’t even stack up to a slap on the wrist.
“No wonder the company are gloating. Chris Grayling (the transport secretary) has let them off the hook big-style.
“This is yet another case of the government and their rail industry cronies investigating themselves while the services they are responsible for are a global laughing stock.”
Southern has been embroiled in a bitter dispute for more than a year with the the RMT and Aslef unions over driver-only operated trains.
The Association of British Commuters (ABC) took legal action over what it described as a “fiasco”.
Southern says it has never made a profit on the service.