Rail passengers will stage a protest today as hundreds of services are removed from the timetable amid a continued shortage of staff and threat of industrial action which have caused travel misery for weeks.
Southern Railway said the interim move, cutting 341 trains a day for a month, was aimed at making services more "resilient".
Commuters who have faced several weeks of chaos because of delays and cancellations, will hold a demonstration at London's Victoria Station later.
Alex Prosser-Snelling, one of the organisers, said: "We aren't people who protest normally, but everyone's fed up of the service.
"Southern mismanagement is needlessly wrecking passengers' evenings, interfering with childcare, and stressing out the workforce. Southern needs to get a grip - and if they can't or won't, the Government shouldn't let them run a railway."
Southern passengers have complained about not getting home from work to see their children because services have been so unreliable and some have lost their jobs.
Southern, owned by Govia Thameslink Railway (GTR), blames high levels of staff sickness as well as industrial action by the Rail, Maritime and Transport union in a dispute over the role of conductors.
The union has offered to suspend industrial action for three months if the company pulls back from implementing the changes from August 21.
The rail industry and the Government have offered support to Southern over its plans to switch responsibility for closing train doors from conductors to drivers.
Rail minister Claire Perry said: "I do understand that train staff worry that the change to roles could be the thin end of the wedge.
"They are concerned that at the end of the GTR franchise a new operator might come in and reverse those promises.
"I want to reassure staff that a busy, growing and successful railway will need more people, not fewer, to help passengers in future. The jobs those people do will be skilled and not dumbed down or contracted out.
"The Government, in specifying future franchises, will ensure that operators are committed to investing in the skills of their workforce, including of on-board staff.
"In return, I ask only that staff and unions help us to modernise and improve services compatible with the modern trains we are introducing for passengers.
"There is no threat to safety, jobs or pay from the introduction of new trains and no excuse left for industrial action. This is now a big test for the RMT - are you on the side of passengers and employees, or needless disruption?"
Paul Plummer, Rail Delivery Group chief executive, said: "We're sorry when passengers are disrupted. Southern's temporary revised timetable should mean more reliable services overall and will help customers plan their journeys better, with more certainty about which trains will run.
"Britain needs a modern railway to carry ever more passengers, and to support housing, jobs and the economy, helping the country to grow and prosper.
"Billions are being spent on new trains, better stations and more services, making up for decades of underinvestment."
More than 12,000 people have signed a petition for the franchise to be removed from Southern.
Two demonstrations have been held at Brighton station and a group aiming to pull together "disenfranchised, angry and desperate" commuters has recently been formed.