The RMT union has already held nine walkouts over plans by rail operator Govia Thameslink Railway (GTR) to change the role of conductors to on-board supervisors.
As part of the changes drivers would open and close the train doors on Southern services.
Now ASLEF, the union representing train drivers, has balloted its members and more than 87 per cent who voted said they were willing to take part in a strike.
Drivers will strike on Tuesday December 13 and Wednesday December 14, Friday December 16, and Monday January 9 to Saturday January 14.
In addition, drivers will not work any non-contractual work from Tuesday December 6.
The RMT is due to hold three-day walkouts starting Tuesday December 6, Thursday December 22, and Saturday December 31.
Mick Whelan, ASLEF’s general secretary, said: “We have done our level best to try and reach a sensible, workable compromise with Southern in the interests of passengers as well as staff.”
“We have always been happy to talk to the company, and we have always believed it is, or should be, possible to do a deal – as we did with ScotRail in Scotland – but it takes two to tango and the company has not been prepared to negotiate.”
Charles Horton, Govia Thameslink Railway’s chief executive officer, said: “Passengers will be rightly furious that these wholly unnecessary and unjustified strikes have been called in the run up to Christmas and in the New Year.
“The travelling public has endured months of misery and seen their work and family lives turned upside down by RMT’s futile industrial action with conductors.
“Now Aslef and the drivers want to compound that suffering by joining the fray in launching more pointless strikes.
“It’s perfectly safe for the driver to have sole responsibility for the operation of a modern train, and that’s how a third of the trains up and down the country - with the full agreement and support of Aslef - already operate today.
“These strikes will have a devastating impact on the South East economy and people’s everyday lives which will bring Southern to a standstill.
“We urge the union to get round the table with us to continue our talks and resolve their dispute without causing further unnecessary grief to passengers.
“Passengers have made it crystal clear that they want an end to these strikes.
“Both the RMT and Aslef should take stock and listen, if not to us, then at least to the travelling public. Let’s end these strikes now without further suffering.”
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