Andria Allan Rudy travelled on the trains between Hove and London

Andria Allan Rudy, 36, from Hove, said the lack of facilities on board Southern trains had caused her distress and embarrassment.

She used to spend two hours commuting to London but said the problem forced her to take maternity leave early.

Southern Railway said it was not legally obliged to provide toilets.

Mrs Allan Rudy, who is eight-and-a-half months pregnant, said even the disabled toilets were often out of use and she had regularly complained to the guards.

'Engineering problem'

"They would often say sorry and there was a problem with the engineering, or there wasn't anybody available to clear them out overnight," she said.

National rail consumer watchdog Passenger Focus said passengers should be able to find working toilet facilities on trains.

"Certain groups of people... do actually need to use the toilet from time to time and if they're not there, then obviously that's a problem they have to face," said spokeswoman Sharon Hedges.