A row over bosses' pay has flared ahead of crucial talks aimed at resolving a long running dispute over staffing on the railways.
Members of the Rail, Maritime and Transport union on Southern Railway are protesting at plans to change the role of conductors.
The conflict has led to strikes and ongoing delays to some of the busiest routes in the country.
The company says high sickness absence levels are affecting services. The RMT claims train crews have been turning up to find that their service has already been cancelled.
The two sides will meet this week at the conciliation service Acas in a bid to break the deadlock.
The union claimed that bosses of Southern's owners the Go-Ahead Group, with the franchise run by Govia Thameslink Railway, have been paying themselves and shareholders "huge sums and bonuses."
Part of the bonuses were to reflect achievements including the "successful mobilisation" of the GTR franchise, said the RMT.
General Secretary Mick Cash said: "It is truly shocking that part of the bonuses paid by the British passenger to the bosses of GTR is down to their "successful mobilisation" of the current franchise.
"Commuters paying up to £5,000 a year for these failing service will be rightly furious. These bonuses are truly money for old rope.
"RMT has revealed that GTR are already being allowed to increase cancellations by a third to 32,000 under its new contract with the Government and now we find that the top brass at this basket-case franchise are on a one way ticket to the bank as well.
"This situation is a national disgrace."
The company said it did not want to respond.