A RAIL union says this seemingly-innocuous picture of a tomato plant reveals a rail operator’s dirty secret – the amount of human waste flushed on the lines every day from train toilets.

The RMT union says the plant, spotted on the Greater Anglia line, near Rochford, grew in waste flushed from trains running between Southend and Liverpool Street.

The union is calling for a ban on train companies running trains with toilets which empty directly on to the lines. It says it is a serious health hazard for track workers and creates disgusting conditions for staff and public alike.

RMT General Secretary Mick Cash said: “It shames Britain's railways that tons of human excrement are being dumped straight on to the tracks while private train companies make huge profits and the Government does nothing.”

Greater Anglia has acknowledged the problem and says its newer trains do have tanks to retain waste. The problem, it suggests, will lessen as older rolling stock is replaced.