Image copyright PA Image caption Staff shortages and industrial action over the role of conductors have caused months of disruption on the Southern network

Southern Railway workers are to stage 14 days of strike action in five blocks in the long-running dispute over the role of conductors on trains.

The RMT union said the latest strikes would begin next month.

It said it had no alternative but to take action over what it called Southern's "blatant disregard for the safety and security of passengers and staff alike".

Southern's parent company said the RMT's action was "shameful".

Five sets of strike dates have been announced by the RMT:

00:01 BST Tuesday 11 October to 23:59 BST Thursday 13 October

00:01 BST Tuesday 18 October to 23:59 BST Thursday 20 October

00:01 BST Thursday 3 November to 23:59 BST Saturday 5 November

00:01 BST Tuesday 22 November to 23:59 BST Wednesday 23 November

00:01 BST Tuesday 6 December to 23:59 BST Thursday 8 December.

The dates include the night of Lewes bonfire celebrations when tens of thousands of people travel to the East Sussex town, many by train.

Months of industrial action by the RMT and high levels of staff sickness have hit Southern's services, which link London with Surrey, Sussex, Kent and Hampshire.

The operator cut 341 trains out of 2,242 from its timetable on 11 July, but has since reintroduced some services.

'Vital role'

RMT general secretary Mick Cash said his members were taking industrial action in a bid to maintain a safe and secure service.

"Govia Thameslink and the government have made it clear that they have no interest in resolving this dispute," he said.

"Instead they have begun the process of bulldozing through the drive towards wholesale driver only operation without agreement.

"Last week there was a train derailment near Watford that involved two trains.

"The guards on both trains played a vital role in protecting the passengers and the trains in what were extremely frightening circumstances."

The RMT wants Southern and its parent company Govia Thameslink (GTR) to agree a similar deal over guards to one reached with Scotrail last week.

Image copyright Getty Images Image caption Southern services have been disrupted by strike action for months

GTR said targeting Lewes bonfire night celebrations was a "cynical ploy" and a "comprehensive and fair offer" had been on the table for weeks.

"The union leadership's claims about jobs, pay, safety are trumped-up make believe," said passenger services director Angie Doll.

"This scaremongering by the RMT is a contrived attempt to gain public support when it knows its spurious arguments about jobs, pay, accessibility and safety have been demolished by independent experts and analysis and are falling on deaf ears."

Rail Minister Paul Maynard said it was unacceptable that passengers' lives would again be disrupted with "unjustified" strikes.

"The travelling public must not be treated with such disdain by unions, and I urge the RMT to call this action off," he said.