Vandals have daubed graffiti across the first set of a £216 million order of train carriages just delivered to their new owner.

The nine carriages were undergoing trial runs from Brighton to Eastbourne after a major investment by rail company South Central.

Fitted with sophisticated air conditioning and illuminated route displays, the new units were brought in to improve travel for rail passengers across Sussex.

Graffiti vandals broke into the sidings behind Brighton station and covered the new Electrostar units with slogans and tags before the carriages could carry a single passenger.

South Central said the damage will cost hundreds of pounds to repair.

Security at the Lovers Walk depot has now been tightened.

Leading figures and rail travellers in Brighton and Hove were disgusted by the vandals' actions.

They said the graffiti presented a poor image of the city for residents and visitors.

Brighton Kemp Town MP Des Turner, a regular train user, said: "I deplore this kind of vandalism. It is not good for Brighton and Hove.

"A lot of investment has been put into these new trains. It is unfair on the railway company and the travelling public for them to be vandalised in this way."

Brian Oxley, leader of the Opposition on the city council, said: "I was appalled when I saw the graffiti-ridden train.

"I have been told by a railway worker that graffiti vandals have been daring each other to daub the new trains and there has been a competition on the internet to see who could be the first to daub them.

"These things must be nipped in the bud before they get out of hand. At last we have a company putting investment into this line and we don't want this spoiled by graffiti vandals."

Simon Fanshawe, who fronted the Place To Be campaign that helped Brighton and Hove gain city status, said: "This is not art. This kind of vandalism does not do the image of Brighton and Hove any good. I hope they catch the vandals and make them repaint the trains."

Hove MP Ivor Caplin, who has been campaigning for new rolling stock and investment on the Brighton line, was appalled at the vandalism.

He said: "This type of behaviour is unacceptable. People should grow up and realise that climbing up to carriages with spray cans close to live electric rails is a highly dangerous practice.

"We want to see these carriages kept in good condition so they can be used for the purpose they were built for, transporting people."

Paul Elgood, leader of the Liberal Democrat group on the city council said: "It does not look good for the city when the first thing rail passengers see when they enter Brighton station is a new train covered with graffiti."

The carriages, which make up three trains, were delivered to Brighton last month. They are the first of the multi-million pound order of 240 carriages, which will eventually replace the entire stock of the South Central fleet operating between London and the Sussex coast.

South Central spokesman Marsid Greenidge said: "We are very concerned the new units have been targeted before they even entered public service. They will now have to be cleaned at a considerable cost.

"We have already tightened security and our message to the vandals is keep away from our depot - you could get injured or killed."