Members of the Rail, Maritime and Transport (RMT) union will walk out on February 22 and March 9 and 16, causing disruption to some of the busiest train services in the country, including those into London Waterloo.
Workers voted by 88 per cent to continue with the long-running industrial action, after the union re-balloted its members to comply with legislation.
General secretary Mick Cash said RMT members had stood “united and solid” in the union’s campaign to retain guards on all trains.
“It is a disgrace that South Western Railway have yet again opted to play for time over the past six months rather than acting responsibly and getting round the table with the union to work out a solution to this dispute that puts safety and the guard guarantee centre stage,” he said.
“That is the package we have successfully negotiated in both Wales and Scotland and on a number of English franchises. It defies belief that we are being denied the same positive outcome on the South Western Railway routes.”
The ballot result was announced a day after the union suspended strikes on Arriva Rail North after securing a deal in the same dispute.
A South Western Railway spokesman said: “We are obviously very disappointed for our customers that the RMT union plans to continue this needless industrial action.
“We have repeatedly committed to rostering a guard on all our services, the same assurance that seem to have been sufficient for the RMT to suspend its strikes elsewhere in the country only yesterday.
“No jobs are at risk and our plans over the course of the franchise mean we will need more guards, not fewer.”
Mr Cash added: “Once again SWR are playing with words and trying to con the public. Rostering a guard and giving a guarantee that all trains will have a guard on board – the assurance we have had from Northern and other operators – are two completely different things.
“SWR are trying to create a loophole they can drive an unlimited number of driver-only trains through and they know it. They should stop playing games and start getting serious”