Members of Aslef will refuse to work overtime from the end of the month after the breakdown of talks aimed at resolving a year-long dispute over staffing and driver-only trains.
As part of the changes drivers are responsible for opening and closing train doors, while conductors are transferred to the role of on-board supervisors.
In its dispute with Northern, Mr Cash said the union was "angry and frustrated" with the company's planned policy of a minimum of 50% DOO trains.
The union said its decision to announce fresh industrial action comes in response to Southern revealing during Monday's negotiations that more than 8,000 trains a year will run without an OBS.
The union has raised safety concerns about the potential loss of a second safety-critical member of staff on services.
'The RMT's proposals would mean cancelling trains and reducing service levels to our passengers.
The RMT confirmed Tuesday, that guards and drivers on Southern Rail will strike again in the on-going disputes over the safety impact of the extension of Driver Only Operation and the removal of guards from services.
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Richard Allan, Northern's deputy managing director, said it was "frustrating" that more strikes had been called and added: "RMT's dispute will not be solved by unnecessary strike action, but instead by working with us to deliver the modern trains, services and stations our customers want".
"Our service levels are stabilising at the highest we've seen in years and we can not agree to anything which will jeopardise running trains and the service to our passengers".
"W ask the RMT to help us to underpin and maximise train frequency and capacity now and for the future".
Govia says Southern ran 95% of its services during the last RMT strike, on April 8.
Paul Plummer, chief executive of the Rail Delivery Group, said: 'More attempted RMT strike chaos would be bad for the economy, businesses and passengers who have already been affected by previous efforts to disrupt the Grand National and the Tour de Yorkshire'.
The RMT General Secretary, Mick Cash, welcomed "Labour's commitment to British state ownership of our rail, power and water, as opposed to the foreign state-backed exploitation of our essential services".
Since privatisation, passenger numbers on the UK's railways have doubled.
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