A vandal is being hunted on suspicion of attempted murder for throwing a bicycle on to rail tracks, causing £10,000 damage to a train and putting the lives of hundreds of passengers in danger.

Police said the suspect, who has vandalised the same stretch of track three times, would be responsible for any lost lives if he was not stopped.

His campaign began in October when he threw a bicycle on to the line at Christ's Hospital train station.

British Transport Police thought it was a one-off incident but last month there were two similar acts in a week.

On January 15 a train hit a bicycle, which caught in the mechanism of the Southern passenger train and caused £10,000 damage.

Exactly a week later a train hit a plank of wood, which had been deliberately placed on the line.

Officers have CCTV footage of a suspect they are keen to identify.

Inspector Gary Ancell said: "We don't know why he might be doing this. Maybe he has something against ticket prices or trains. This is dangerous for the person and, more importantly, for train staff and passengers because he could derail a train.

"We are looking at attempted murder. The courts can impose a life sentence for this. We need to get this suspect identified and interviewed as soon as possible."

In the past year there have been 25 acts of trespass and vandalism on Sussex tracks, about one every fortnight.

Five were committed in the first three weeks of January. Two of those were at Christ's Hospital and others were at Seaford and Battle.

A fifth incident occurred at Norman's Bay, Pevensey, when a woman drove a car on to the train track after being directed there by a satellite navigation system.

Last June two young boys narrowly escaped death at Tidemills crossing near Newhaven. They were spotted on the tracks by a vigilant train driver. The driver bought the train to an emergency stop and a tragedy was averted.

Three teenage girls were arrested and cautioned after they were seen wandering down the side of the track between Shoreham station and the railway crossing at Dolphin Road last April.

A teenage girl was charged with trespass after being caught walking along rail lines in St Leonard's. Disruption was caused to several trains after transport workers cut power to the lines.

Insp Ancell said Ifield in Crawley and Hampden Park in Eastbourne were vandalism hotspots, as well as Christ's Hospital. He added transport police would step up patrols this half-term week. He said: "We ask parents to make children realise how dangerous railway lines are and make sure they know where they are over half-term."

Anyone with information about the vandalism at Christ's Hospital should contact British Transport Police on 01273 228159.