Rail passengers say short rush-hour trains are forcing them to endure cattle truck conditions at the end and start of some journeys.

Sussex rail operators Thameslink and SouthCentral are coming under fire for running the short trains at peak times.

One of the worse cases of overcrowding is on the 8.36am Brighton to Bedford Thameslink service, which is the main service for workers in the City of London, who need to be at work around 10am.

The train has been reduced to a single four-car unit with most commuters standing from Haywards Heath onwards.

Thameslink say commuters will have to endure another month of misery as units are still being repaired following flooding at Farringdon at the beginning of August.

SouthCentral has also been guilty of running shorter trains on some of its peak morning services, such as the 7.33am Brighton to London Bridge, forcing commuters to stand once services reach Haywards Heath or even Burgess Hill.

The shorter trains coincide with the timetable changes earlier this year which saw a cut in the number of morning rush-hour trains to London from Sussex.

Journalist David Edwards, 29, who commutes to London Bridge from Brighton said: "Not only do we have fewer trains, which take longer to reach London, we now have shorter trains and more overcrowding. Sometimes we are travelling in cattle truck conditions.

"People are paying more than £250 a month to commute to London only to have to stand for a large part of the journey on filthy trains with already appalling delays. We were promised a better service from SouthCentral and Thameslink."

Shelley Atlas, chair of Brighton Commuters, said: "The rail companies should do all they can to run trains with the maximum number of carriages during rush hour."

Commenting on the cause of the disruption, Martin Walter, communications director for Thameslink, said: "Some of the units were stuck in five feet of water and it completely damaged the electrical system.

"You can't suddenly replace these units like you can a car.

"If we brought the units back too early and they failed again, there would be further problems.

"If we ran longer units on some rush-hour trains, it would mean shorter units on others.

"The units are currently being repaired and tested at our Selhurst depot and we hope to have them back in full working order in about a month's time."