A “flagship” train service between Brighton and London has been scrapped after a last minute decision by the rail regulator.

Southern Rail had been due to launch its new service of four fast hourly off-peak trains next month.

However, the Office of Rail Regulation (ORR) put a halt to the changed timetable just three weeks before it was due to begin.

Southern said it was “frustrated” by the decision but it has been welcomed by rail campaigners East Sussex Rail Alliance (ESRA) who said services from other areas would have suffered, leading to more overcrowding and slower trains.

A Southern spokesman said: “We are very disappointed for our passengers who would have benefited from this additional service and we are now turning our attention to the May 2011 timetable change to consider how we can move forward with similar improvements at that time.”