UPDATED: ASLEF is reported to be planning an indefinite overtime ban on Southern as part of the continuing dispute over driver-controlled operation. 

The start date is not yet known, but the reports follow the announcement of a 24-hour strike by the RMT on 30 May on Southern, as well as on Merseyrail and Northern. The RMT said ASLEF's decision was 'important', and has called for new joint talks.

Govia Thameslink Railway chief operating officer Nick Brown said: “After over five months of intense negotiations and two peace deals agreed and recommended by the ASLEF executive, we are dismayed the union leadership is taking this action, which is designed to impact as many of our passengers as possible.

“Driver-controlled operation with on-board supervisors was fully implemented back in January and thanks to this we are running more trains than before and our service has improved for five consecutive months. We’re safely running over 80,000 trains a month with drivers controlling the doors across our network – we’re sorry that passengers will suffer as a result of this unnecessary action.

“We have worked our hardest to resolve this dispute with ASLEF. If this action does go ahead we will run as full a timetable as possible. We will be working around the clock to evaluate the impact and develop contingency plans which will be advertised as soon as possible.”

RMT general secretary Mick Cash said: “This is an important and significant development and RMT would now call on GTR to join ‎with both unions in tri-partite talks aimed at negotiating a settlement to this dispute which puts safety and access to services at the top of the agenda.”