The train operator of one of the busiest rail networks in Britain is set to axe 350 services a day.
The RMT was shown the amended timetable in a meeting with parent firm Govia Thameslink (GTR), which owns Southern Rail.
GTR said its amended timetable would be a temporary measure until staffing returned to normal.
Union general secretary Mick Cash told the BBC: “This latest savage attack on passenger services by GTR is nothing to do with staff sickness and everything to do with gross mismanagement of this franchise and the failure to employ enough guards and drivers to fill the current rosters and diagrams.
“The continuing attempt to blame the front-line workforce for this crisis is a cynical and cowardly ploy that will not wash with the travelling public.”
Under the revised timetable services from Clapham Junction to Milton Keynes and Tonbridge to Redhill will be completely removed, and trains will be removed from the Littlehampton to Portsmouth & Southsea, Brighton to Southampton and Brighton to Seaford services.
