Rail passengers in Sussex could face strike chaos as thousands of workers are balloted on industrial action.

Staff at more than 20 rail firms are to vote on industrial action in a long-running row about the role of guards.

The workers involved include those at Connex South Central and South West Trains, both of which serve Sussex passengers.

Thousands of members of the Rail, Maritime and Transport Union (RMT) will be sent ballot papers next week after the dispute unexpectedly flared up.

The union has complained that guards have less responsibility under rule changes introduced more than a year ago.

At the time the union warned guards would eventually be reduced to the role of "KitKat sellers" and balloted workers in 23 train companies, with 16 voting to strike.

The threat of a walkout was called off in March 2000 but the dispute was never resolved.

An RMT spokeswoman said: "This is a national dispute and it is about the operational safety of train crews. It is to do with guards and we have concerns about their safety."

Meanwhile, a strike by rail guards was causing further problems for other travellers today.

Union members on South West Trains (SWT) will stage a 24-hour strike over the "total breakdown" of industrial relations. Services between Brighton and Portsmouth are subject to disruption.

Talks during the bank holiday weekend failed to resolve the row.