Rail union RMT has confirmed a new round of industrial action involving Southern Rail guards after "a point blank refusal by both the company and the government to engage with the union" ahead of a 21 August deadline.
Guards will not work any shifts between 12:01AM on Monday 8 August and 11:59PM on Friday 12 August.
RMT said that it had offered a three month pause to action if the company "took the gun away from the guards heads and agreed to suspend their proposals and allow space for talks to take place", but "that request has been kicked back in our faces".
The union also said it had written to transport secretary Chris Grayling asking for direct talks, but the letter was "ignored".
Therefore, said the union, "with the downgrading of the safety-critical role of the guards due to be railroaded through on the 21 August the union has no option but to confirm a new programme of action to defend jobs and safety."
RMT General Secretary Mick Cash said: "This action has been forced on us by the arrogance and inaction of Govia Thameslink and the Government who have made it clear that they have no interest in resolving this dispute or in tackling the daily chaos on Southern.
"Our fight is with the company and the government who have dragged this franchise into total meltdown. We share the anger and frustration of passengers and we cannot sit back while jobs and safety are compromised on these dangerously overcrowded trains.
"It is disgraceful that neither the company or the Government are prepared to engage and are looking to bully through the extension of DOO and the attack on the guards set for 21 August. They should wake up and get round the table now as an urgent priority."
London mayor Sadiq Khan recently called for Transport for London to step in and take control of Southern until its problems can be resolved, after the rail company said it would cut 341 trains a day in response to prolonged cancellations and delays.
Meanwhile, independent transport regulator London TravelWatch has called for an independent review of Southern, citing concerns about the "continuing poor performance and unreliability" that customers are facing.