A 27-day rail strike during December and New Year will go ahead after two days of talks ended without agreement.
The Rail, Maritime and Transport (RMT) union said its members at South Western Railway (SWR) will walk out in a long-running dispute over guards on trains.
RMT general secretary Mick Cash said it was “increasingly clear” SWR was “not interested in reaching a settlement”.
SWR said it had promised to keep guards on trains and would do everything possible to keep customers moving.
It previously said the union was “purely focussed on keeping control of train doors in a misguided attempt to hold power over the industry”.
Mr Cash said: “Throughout these talks SWR have not shown any intention of moving the issues at the heart of the dispute forwards despite verbal assurances in earlier discussions.”
SWR managing director Andy Mellors said: “We promise that there will always be a guard on our trains. We also promise our guards will maintain a safety critical role on our trains.
“We believe that these promises deliver what the RMT has been asking for, so these strikes are unnecessary.”
Strike days are as follows:
SWR is due to release a revised timetable next week.