Passengers travelling to, from and via Gatwick Airport faced chaotic scenes at the weekend as train operator Southern was accused of failing to lay on enough buses.
The rail replacement buses were needed as a section of track between Gatwick and Three Bridges was closed for repairs.
The scenes were similar to those at Redhill recently and which drew criticism in Parliament.
Anthony Smith, chief executive of the independent watchdog Transport Focus, said: “Passengers will rightly be frustrated to find they can’t travel on the bank holiday weekend.
“These works and the weather were no surprise – so why has Southern failed to provide enough rail replacement buses?
“We’ll be working with the operator to find out what went wrong and to ensure that passengers aren’t left high and dry next time they plan a trip to the seaside on a weekend.”
At the weekend Southern posted a warning on its website about the delays.
It said: “There are currently large queues for the replacement bus services at Gatwick Airport and overcrowding at the station.
“As a result, customers should anticipate extended journey times and cancellations between London Victoria and Gatwick Airport to prevent further overcrowding.
“Services from Brighton towards London Victoria after 5pm are expected to be extremely busy and journey times to be extended as a result.”