Hundreds of thousands of rail passengers face a week of misery after talks aimed at resolving a bitter row over the role of conductors broke down.
Southern Railway will introduce an emergency timetable for five days from Monday, running just 60% of its services across London and the South East.
Three days of talks between the company and the Rail, Maritime and Transport union at the conciliation service Acas collapsed.
The two sides blamed each other for the continued deadlock, while the union accused the Government of "sabotaging" the talks.
The company's Passenger Service Director Angie Doll said: "We have gone the extra mile with our compromise offer, but the RMT has made it clear they are not prepared to negotiate. They did not want to discuss the role of the on-board supervisor and remain rigidly opposed to evolving the role of on-board staff to focus more on customers.
"We are deeply disappointed and angry on behalf of our passengers at this stance, which will cause misery for our passengers and untold damage to the local economy in the south east.
"The RMT's strike is unnecessary, unacceptable and unjustified."
RMT general secretary Mick Cash said: "It was clear right from the start of these talks that there was no serious intent from Govia Thameslink to engage in genuine negotiations and that their script was being written from behind the scenes by their Government paymasters.
"I have been involved in countless negotiations and have never witnessed a farce like this."
The union said it was told by industry sources that Transport Department official Peter Wilkinson, who told a public meeting he wanted a "punch up" with rail unions was responsible for "wrecking" the talks.
Southern, part of the huge Govia Thameslink Railway (GTR) franchise, said an offer by the union to suspend industrial action if the company agreed to terms put forward by ScotRail to resolve a separate dispute, was a "complete red herring".
Ms Doll said: "This amounts to a continuation of the current operating model and delivers none of the punctuality and customer service benefits we are determined to deliver to our passengers".
Rail Minister Paul Maynard said: "This unjustified strike action from the RMT will do nothing other than cause five days of misery for passengers. It is deeply disappointing that union bosses continue to overlook the impact they are having on hardworking people who want to get on with their journeys.
"The changes GTR are proposing will modernise services and provide better journeys. Rather than working with the operator to resolve these issues, the RMT has clearly decided that it is not on the side of the passenger."
Paul Plummer, chief executive of the Rail Delivery Group, representing train operators and Network Rail, said: "This strike action will cause misery for thousands of passengers. The offer to staff set out by Southern demonstrates there are no risks to jobs or pay. We already know that drivers operating the doors on trains is a safe way of working.
"The rail industry has to modernise to deliver the better service today's customers expect and deserve. At the heart of this dispute are changes that would mean a better on board service for passengers and less disruption when problems affect the railway. In the interests of passengers, it's time to implement these changes and end this dispute."