Workers on Southern Railway are "solidly supporting" the start of a five-day strike which will cause travel misery for hundreds of thousands of passengers.

Members of the Rail, Maritime and Transport (RMT) union have walked out, mounting picket lines outside stations, in an escalating row over the role of conductors.

Southern's owner, Govia Thameslink Railway, apologised to passengers, describing the strike as "completely unjustified".

Some parts of Surrey and Sussex will have no trains at all because of the industrial action.

Talks at the conciliation service Acas collapsed last Friday.

The union had offered to suspend industrial action if the company agreed to an offer like the one made by ScotRail in a similar dispute but Southern said this was a "red herring".

RMT general secretary Mick Cash said: "The strike action this morning is rock solid across the Southern Rail network as we fight to put rail safety before the profits of the failed Govia Thameslink operation.

"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.

"We offered to suspend the action on Friday if they matched the offer we secured on ScotRail. They kicked that back in our faces.

"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."

An emergency timetable has been put in place, with Southern saying it will run 60% of services.

Trains have been disrupted for weeks because of industrial action and a shortage of staff, which the company has blamed on high levels of sickness.

The union has accused the Government of "sabotaging" the Acas talks.

Govia Thameslink Railway (GTR) said it had offered new assurances on jobs to the union, although it is pressing ahead with plans to change the role of conductors later this month.

Chief executive Charles Horton said the strike was "completely unacceptable, unjustified and unnecessary".

In a message to passengers, he said: "We want to run new and modern trains to provide more space and capacity and we want to make essential changes to how we operate, including giving our drivers responsibility for closing train doors so that on-board staff can focus on helping you during your journey."

Bruce Williamson, a spokesman for the Railfuture passenger group, said: "It is unfortunate it has come to this. There needs to be some serious banging of heads.

"Commuters will suffer. It is not good for the rail industry. It does not inspire confidence in the rail industry as a transport mode and it damages the credibility of the network as a whole.

"There is generally a problem with overcrowding and resources on the railway, so then adding on a strike is a double whammy for customers.

"I am wondering if this is an opportunity for (Transport Secretary) Chris Grayling to get involved. He is new to the job and might be able to act as an intermediary and bang some heads."

mfl Page 4: 08:23 The RMT condemned "lies and smears" over the Southern Rail guards ballot, pointing out that 393 members were balloted, with 321 voting (81%) and 306 backing strike action (77% of the total members).

"These numbers easily outstrip the hurdles proposed for union ballots by the Tory right in terms of both turnout and the majority in favour of action," said a union statement.

Mr Cash said: "The turnout was over 80%, and 77% of our total membership voted yes. That is a mandate the politicians could only dream of.

"It's interesting that no-one ever challenges the mandate of the unelected and unaccountable GTR bosses who have unleashed havoc on their passengers for months."

The RMT held a number of strikes at ScotRail over driver-only trains but suspended industrial action last week after a new offer.

ScotRail said conductors would be retained on a new fleet of electric trains which are scheduled to start running from next year.

Conductors would also keep their safety role, such as being responsible for evacuating the train in an emergency.

ScotRail had planned to replace them with ticket examiners on some services.

The proposed deal has not been accepted yet, but it was enough to suspend further strikes.

The RMT told Southern last Friday that it would pull back from this week's action if a similar deal was offered.

Q AND A: SOUTHERN RAILWAY STRIKE OVER CONDUCTORS DISPUTE

Southern Railway passengers are facing a week of travel chaos because of a five-day strike by members of the Rail, Maritime and Transport union (RMT) in a long-running row over the role of conductors.

Q: What is the dispute about?

A: Southern, part of the huge Govia Thameslink Railway franchise, want drivers to have responsibility for closing train doors.

Q: Why are Southern doing this?

A: The company says on-board staff will be able to focus on helping passengers, insisting this will offer a better service.

Q: Will any jobs be lost?

A: Southern says no jobs will be affected, pay will not be reduced, and the same "safe and tested" method is already in operation on 40% of its network.

Q: So why is the RMT opposed to the move?

A: The union believes safety would be affected if the role of conductors is changed, especially with the relentless rise in passenger numbers.

Q: Does the union accept the assurances on jobs?

A: The RMT is suspicious that giving responsibility to drivers will downgrade the role of conductors and could lead to job cuts in the future.

Q: Is the strike being well supported?

A: The turnout in a ballot of members was 81%, with 77% backing action, well above the threshold being brought in under the new Trade Union Act. The RMT said today's walkout was being "solidly" supported.

Q: Was any progress made at last week's talks?

A: The two sides spent three days at the conciliation service Acas but the talks collapsed, with a deal further away than ever. No more talks are planned.

Q: How bad is the disruption?

A: Southern had already cut 341 trains from its timetable because of staff shortages and will only run 60% of trains this week.

Q: How are passengers reacting?

A: Southern has faced criticism for months because of delays and disruption, with a number of protests held by commuters and other travellers.

Q: Is Southern facing any more strikes?

A: Two other rail unions are balloting for industrial action - the TSSA over ticket office closures and the drivers' union Aslef over claims of a breakdown in industrial relations.

Q: Is the Government doing anything to resolve the dispute?

A: Ministers have condemned the union for the strikes, but the RMT has accused the Transport Department of "sabotaging" last week's talks.