The train drivers union ASLEF was forced to call of its ballot for strike action at Southern at the weekend because voting papers were sent to some of the wrong members, it is understood. It would have meant the result would have been open to a legal challenge by the company.
The ballot over drivers closing train doors started on Friday and was halted the following day.
The union executive will meet today and is expected to order a new ballot with strike a tom possible around Christmas.
Drivers are being balloted on plans for so-called DOO, driver only operation. They will in future close train doors rather than guards which it is claimed is unsafe. Southern say that is not true and want guards to spend more time with passengers.