Southern rail's parent company has said it will take legal action against train drivers' union Aslef to the Supreme Court over persistent strike action.
In a statement Govia Thameslink Railway (GTR) said: “GTR is determined to protect its passengers and its business from unlawful industrial action. GTR is therefore prepared to continue its legal claim to the Supreme Court, as it believes that it has an arguable case that the industrial action is unlawful under EU law.”
The train operator tried to take legal action against the Aslef strikes in December, but the High Court ruled in Aslef's favour.
Aslef has been approached for comment.
The industrial action is over a dispute concerning the operation of train doors on Southern rail services.
Walkouts on the Southern network have been undertaken by both Aslef and the Rail, Maritime and Transport (RMT) union. According to research by online estate agent Emoov, the strikes have affected house prices along Southern's lines.
It comes amidst the latest batch of Southern strikes - over three days this week.
Southern has been advising passengers to avoid all travel unless it's essential as no services will be running. Commuters were braced for more trouble as Southern warned: "Anyone who does travel should expect to queue, plan for longer journeys and realise the service they join will be exceptionally busy."
Previous talks at conciliation service Acas failed to resolve the dispute, which the government has called "politically motivated" and "designed to cause maximum disruption".
In a letter sent to MPs on 5 January, transport secretary Chris Grayling reiterated his views that there were "political motivations" for the industrial action on Southern rail. He also said: "The fact that this is a strike that has been ruled as legal by the courts also makes it difficult to force a resolution."
Earlier this week, Labour leader Jeremy Corbyn said he'd join a Southern rail picket line, saying he felt long-suffering commuters would support his position.
"Yes I would, because I think Southern rail have behaved in a terrible manner, and the government seems to be more interested in protecting Southern rail despite its appalling service and shortage of trains, overcrowding and all that goes with it, and continued allowing them to run the franchise on Southern," he said.
Planned Southern rail strike dates:
- Friday 13 January
- Tuesday 24 January
- Wednesday 25 January
- Friday 27 Janaury