A fleet of new trains ready to roll into Sussex won't be able to use London Victoria because they could set off fire alarms and force an evacuation.

Bosses at train operator South Central blamed a combination of fumes from their multi-million pound Turbostar diesel trains and the London terminal's low ceilings.

The blunder was revealed as the rail bosses showcased the Turbostars in Derby, where they are being built.

It means South Central trains to the capital from Uckfield will have to stop at London Bridge instead of Victoria.

Victoria's ceilings have been lowered to make way for a huge shopping mall above. London Bridge has a higher ceiling and the problem of fumes will not arise.

Charles Horton, South Central's managing director, said: "At present, diesel trains can only use certain platforms at Victoria but these new trains are so sophisticated and slightly higher. They set off the alarms and could cause alerts."

The new trains, with their airline-style seats, will be gradually introduced on the Ashford-Hastings line from the end of this month. They will be brought on to the Uckfield line next year and in 2005.

There will also be a new Brighton-Ashford service, giving the city a direct connection to the Channel Tunnel rail link.

The arrival of the new diesels means South Central is unlikely to electrify the Hastings-Ashford line.

Mr Horton said: "These new trains will provide a whole new travelling experience for our passengers. For the communities in Uckfield and Ashford and Hastings, the arrival of modern trains is long overdue."

The rail company believes the sophisticated diesels with air-conditioning and electronic route displays can provide as good a service as trains on electrified lines.

The old diesels on the Uckfield and Ashford-Hastings lines were some of the most decrepit in operation. They have been in use for more than 50 years and were affectionately known as "thumpers".