Police and train drivers are warning lives are at risk from graffiti vandals.

They spray their tags on bridges and trackside buildings throughout the Sussex rail network.

A Brighton-based driver said the vandals are now defacing speed limit and other warning signs.

The driver, who does not want to be named, said: "Lives are being put at risk by these people.

"The signs are reflective so that they can be seen at night.

"If they are sprayed over drivers will not be able to see them and the consequences could be horrific."

He said that train drivers can be disciplined for exceeding a warning sign by just 2 mph.

And they can be sacked for driving more than 5mph over the limit.

He added: "A driver could lose his job because of some little herbert with a spray can.

"Worse still, somebody could die if there is an accident as a result of a sign being missed.

"The Thameslink route through London which is used by thousands of Sussex commuters is particularly bad at the moment."

Inspector Mick Morriss of British Transport Police said the problem of trackside graffiti was taken very seriously.

Surveillance cameras are used to keep watch for people spraying trackside buildings.

Insp Morriss said: "They tend to go more for bridges, buildings and trains rather than signs.

"It amazes me how they get to some of the more inaccessible places.

"It is very dangerous and a man lost his arm when he was hit by a train while spraying a bridge near Gatwick two years ago.

"We have had a number of successes catching and prosecuting people responsible for graffiti recently.

"Last month a 17-year-old boy was sent to a young offenders centre for 28 days and another given 100 hours community service.

"They were caught spraying graffiti at Moulsecoomb station."