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 today.
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.
"Standing in the way of modernisation puts this vital upgrade at risk and is against the interests of passengers, our workforce and the country as a whole.
"Britain has Europe's safest and fastest-growing railway, and we cannot afford to fall behind other countries by failing to embrace new technology and new ways of working that benefit our customers.
"Trains where drivers open and close doors are nothing new, and deemed safe by rail safety experts and the independent regulator which oversees safety on the railway.
"It means other on-board staff who are trained in safety are free to help passengers more and to improve customer experience. No jobs or pay will be cut."
Mick Cash, general secretary of the RMT, said: "It is outrageous for the minister to claim that front line Southern rail staff are not on the side of the passengers.
"Unlike Ms Perry, her officials and the GTR bosses it is our members at the sharp end trying to deliver a service against a background of gross managerial incompetence and rank profiteering.
"The disgraceful slurs, abuse and lies being heaped on our members by the company and their cheerleaders in Government have to stop.
"The axing of nearly 350 trains a day by GTR is a crisis measure designed to rig their appalling performance figures.
"The fewer trains you run, the fewer will be delayed and the better your headline performance statistics will look. That is a fix of epic proportions and the public will not be fooled by this chicanery.
"The new timetable also means that the vast reduction in services, approved by the Government, will leave remaining trains dangerously overcrowded and it will be our members at the sharp end ?left to manage the safety of the passengers while the minister and her GTR colleagues are tucked away in their plush offices.
"Despite the timetable fix this remains a franchise in terminal meltdown and RMT will continue to fight for safety-critical jobs, safe services and public ownership and control."
Over 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.
Liberal Democrat leader Tim Farron said the Government assurances were "not worth the paper they are written on", adding: "It's all words and no detail.
"What I would like to see is some clarification on whether or not job roles will change in light of the new specifications of rolling stock, if employees will be moved, and if they will have the same amount of contracted hours."