Conductors on Connex South Central lines are refusing to work overtime or on rest days from Monday in a dispute over pay.

The Rail, Maritime and Transport Union says some trains may be cancelled entirely.

The union says the industrial action is because conductors are paid less for working on their rest days than drivers. Conductors get £12, they say, while drivers get £40.

Connex had opposed the action in court, on the basis of disputed ballot procedures.

'Commuters will be affected'

But they were unsuccessful in the High Court and the Court of Appeal.

An RMT spokesman said the action would last for at least five days.

"This is a five-day ban on overtime which will result in some cancellations.

"Commuters will be affected through cancelled trains.

"The industrial action is a ban on overtime and not a strike. If a conductor is rostered to work on a train on a rest day then that train won't run.

"There is still time this week to negotiate a settlement, but if we don't find a resolution we will have to decide what to do after consulting with members."

Connex spokesman Ken Gibbs said that less than one in three conductors would be involved in the industrial action.

"The only message to our customers can be to turn up as normal tomorrow (Monday).