The bitter dispute over driver-only trains on the c2c line is to escalate after union leaders threatened to ballot members working elsewhere in the country over strike action.

However, the rail company has warned they may be prepared to go to court to halt the action.

The Rail Maritime and Transport Union staged another one-day strike on the Shoebury line into London on Wednesday in protest against the driver-only trains, claiming they will jeopardise passenger safety.

Angry union members claim c2c is training "inexperienced managers" from other rail companies within the National Express group, to carry out guard duties in advance of the next scheduled stoppage on August 1.

Union rep Derrick Marr said: "What we've done is written to all those companies saying if they do not give us an assurance that their employees will not carry out any operational duties on the c2c line, we will ballot our members for industrial action.

"We've set them a seven-day deadline to reply - we're not waiting until August 1 to find out what's going to happen."

Alan Wheeler, c2c spokesman, accused the union of "desperate scaremongering".

He denied people drafted in for the next strike would be "inexperienced managers", but would instead be guards already working on other sections of track who would be trained up to work on c2c's trains.

He warned the union could face a legal challenge if it balloted its members.

The union hailed Wednesday's strike as "the best-supported yet", with just 11 out of 47 trains running for much of the day.

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