A fresh strike by workers on Southern Railway is being “solidly supported”, causing fresh travel chaos for hundreds of thousands of passengers.

Members of the Rail, Maritime and Transport (RMT) union have launched a three-day walkout in a long-running dispute over the role of conductors.

The drivers' union Aslef has started an overtime ban in a separate row over driver-only trains.

Around half of Southern services are expected to be cancelled because of the joint action.

Members of the RMT plan to confront Transport Secretary Chris Grayling when he gives a speech on Tuesday night on the Government's plans to give train operators control of track maintenance.

The union criticised Mr Grayling for not mentioning the Southern disputes in extracts from his speech which were released beforehand.

RMT general secretary Mick Cash said: “Our guards members on Southern Rail remain rock-solid and absolutely determined in their action in defence of rail safety this morning.

“The union repeats its demand for Chris Grayling and his Rail Minister to get out of their bunker, stop the mud-slinging and take up the offer from RMT for direct talks to sort out the worsening crisis on Britain's biggest rail franchise.

“Tonight we will make another attempt to engage with Mr Grayling when he makes his big speech on breaking up and privatising Network Rail at the private Policy Exchange event.

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“Instead of parading around the newsrooms with his lethal scheme to give outfits like Southern a chance to wreck rail infrastructure, as well as our train operations, the Transport Secretary should be in a room with the unions and GTR (Southern's owners) sorting out the current shambles.”