Workers on South Western Railway are to stage three fresh strikes in September after the collapse of talks aimed at resolving the bitter row over the role of guards.

Members of the Rail, Maritime and Transport union (RMT) will walk out for 24 hours on September 2, 8 and 15, on top of a strike on August 18 and a 48-hour stoppage from August 31.

The union accused the company of “sabotaging” talks this week over the long-running dispute, saying SWR had “no intention” of reaching a deal.

RMT general secretary Mick Cash said: “RMT is angry and frustrated that the company’s cavalier and contemptuous approach to talks leaves us no option but to confirm additional strike dates. We know that passengers will share that anger.

“Today SWR have benefited from a fares windfall that will pump up their profits. They have plenty of money to employ guards on their trains and to sign off the guard guarantee the union has achieved elsewhere.

“South Western Railway seem to think they can treat the union and their staff with utter contempt. They need to change that attitude, get serious and put a team in place that can talk with us with authority on the safety, security and access issues at the heart of this dispute.”

A South Western Railway spokesman said: “It is extremely disappointing that the RMT has yet again chosen to needlessly inconvenience our customers, and its own members, across our network.

“We are committed to resolving this dispute and earlier this week met with the RMT at Acas, reiterating our proposed framework agreement which centres around how we can better keep our customers moving during times of disruption.

“Despite the RMT agreeing to a similar deal with another train operator just a few weeks ago, the union has failed to explain to us, their members or our customers why such a deal is not acceptable on our network.

“The RMT executive’s answer to every question is strike, they need to start accepting that the railway is modernising and that their members can play a key part in that future if only they stop calling for action and work with us to deliver a better railway for our customers.

“This decision is totally unnecessary and pointless, we cannot make it any clearer that our plans mean more not fewer guards, we have guaranteed to roster a second person on all our trains and we have guaranteed terms and conditions.

“We will continue to do everything we can to minimise disruption to passengers while the RMT persists with these unnecessary strikes.”