Workers in three rail firms are to stage a series of fresh strikes in bitter disputes over staffing and driver-only trains, threatening fresh disruption for hundreds of thousands of passengers.

Members of the Rail, Maritime and Transport union on Southern, Merseyrail and Arriva Rail North will walk out for between one and three days in the coming weeks in an escalation of the deadlocked rows.

Members of the drivers' union Aslef on Southern are being balloted for strikes in a separate dispute over pay.

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The announcements were made as a delayed report into Southern said its infrastructure is in "poor and unreliable" condition and all elements of the system have been under strain.

The long-awaited report by Network Rail director Chris Gibb criticised industrial action over the past year, but also made it clear that the Department for Transport, Southern's owners Govia Thameslink Railway, Network Rail as well as the unions, have been "well aware" of how much strain the system has been under.