London, Dec 2 (AFP) Union members on one of Britain's busiest railway networks walked out on Monday, on the first day of a planned 27-day strike that could affect hundreds of thousands of commuters.

The Rail, Maritime and Transport (RMT) stopped work on lines run by South Western Railway, which operates lines in and around London, and to towns and cities in southwest England.

Passengers have been warned to face disruption in the run-up to Christmas, as only half of services will run, including to and from Britain's busiest railway station Waterloo.

The planned stoppage -- one of the longest in living memory -- was called after talks broke down between unions and bosses about the role of guards on trains.

South Western wants to hand responsibility for closing doors on trains from guards to drivers, but the RMT says that reduces the role of guards and comprises safety.

RMT general secretary Mick Cash said the guard would become "little more than a passenger in the longer term" and put their jobs at risk "at some point down the line".

South Western called the union's demands "outdated" and said it had offered a "safety-critical role" for train guards.

"Unfortunately, it is clear to us that the RMT is unclear on what this dispute is about and intent on striking no matter what," it said.

Britain's partly privatised rail network is often criticised for scheduling problems and high ticket prices.

On Monday, the main opposition Labour party pledged to slash fares by a third from January next year, and make travel free for under-16s if it is elected at polls on December 12.

Train companies last weekend confirmed they would raise fares by an average of 2.7 percent next year. (AFP)

(This is an unedited and auto-generated story from Syndicated News feed, LatestLY Staff may not have modified or edited the content body)