The Southern Railway dispute continues on Friday as a 48-hour strike gets under way, leading to the cancellation of trains and more disruption to services.
The latest blow for commuters, with a stoppage which got under way at midnight, comes as the company announced fresh strikes over Christmas and the New Year, which are likely to cause travel misery for hundreds of thousands of passengers.
The Rail, Maritime and Transport (RMT) union accused the company and the Government of "sheer pig-headedness" as it announced that its members will strike from 0001 on December 22 until 2359 on Christmas Eve and again from 0001 on New Year's Eve until 2359 on January 2, when new fare rises come into effect.
RMT general secretary Mick Cash said Southern's owners, Govia Thameslink Railway (GTR), and the Government had made it clear they have no interest in resolving the long-running row over the role of conductors.
Services have been disrupted for months, partly due to the strikes, staff shortages and other problems.
A damaged track caused chaos on Tuesday evening, leading commuters to warn of dangerously overcrowded trains and platforms.
Mr Cash repeated his call to Transport Secretary Chris Grayling to "get out of his bunker" and try to help resolve the row.
"This week we have seen repeated chaos on Southern Rail services that has shown once again that they are simply incapable of running safe and reliable services.
"The only obstacle to their removal from their management contract is the Government, who are calling the shots and pulling the strings behind the scenes while publicly claiming the dispute is between RMT and GTR.
"In the light of the continuing public anger at the absolute state of the Southern Rail operation, it is disgraceful that neither the company or the Government are prepared to engage and are continuing to attempt to impose driver-only operation in the interests of putting profit before safety."
A spokesman for Southern said: "Not content with causing months of misery, the RMT has now hit a new low and is determined to cancel Christmas for the travelling public.
"These latest strikes will not just hit families wanting to get home for Christmas but also the shops and businesses for whom Christmas is their busiest time.
"These strikes are spiteful, vindictive and pointless given the majority of conductors have now signed up to the new on-board role.
"This has never been about safety, it's purely about the RMT hanging on to outdated working practices and union power."
Paul Plummer, chief executive of the Rail Delivery Group, representing train operators, said: "More needless strikes by the RMT will be an unwanted Christmas present for passengers they will disrupt on Christmas Eve and at New Year.
"Changes being adopted by Southern, opposed by the RMT, will give passengers a better service."
Southern said it is putting on extra trains during the next strikes, with almost all its 156 stations having either a train or bus service.
But there will be a restricted service, with many routes having fewer trains, and on some routes there will be no trains at all.
There will be no rail service on Saturday to Lewes, where tens of thousands of people attend the town's popular annual bonfire, with Southern citing public safety for its decision.
A fresh row broke out after the union revealed it had received a letter from Southern saying that backdated holiday pay is being withheld from conductors involved in the industrial action until the dispute is over.
Rail minister Paul Maynard said: "It is extremely disappointing that the RMT have announced yet more strikes over the Christmas holidays which will make passengers suffer at a time when they will be travelling to see family and friends.
"The union leaders have continually rejected a deal that means no job cuts and ensures that on-board supervisors will carry on delivering safe, accessible and more reliable rail services.
"I strongly urge the RMT to put passengers first and call off this damaging action."
Anthony Smith, chief executive of the independent watchdog Transport Focus, said: "It is passengers who suffer most in the event of strikes and they will be angry that Southern and the RMT trade union have still not reached an agreement or even a Christmas truce. It is crucial that all parties get back around the table and resolve this matter without bringing the railway to a standstill over the Christmas period.
"Passengers need plenty of information about the strikes and what services will be running to allow them to plan their journeys during this uncertain time."