An early morning train service from West Sussex to London is the most overcrowded in England and Wales, new figures show.
Southern Railway's 7.16am train from East Grinstead to London Bridge typically has 1,366 people rammed into a dozen carriages designed for just 640, Department for Transport (DfT) data shows.
This is a load factor of 213% - higher than any other service.
The DfT said additional carriages cannot be added to the train but when the Thameslink Programme is completed next year there will be extra services on routes south of London to boost capacity.
Other jam-packed journeys making the top 10 overcrowded list include the 6.57am Brighton to Bedford, the 7.55am Cambridge to London King's Cross and the 4pm Manchester Airport to Edinburgh.
The figures relate to standard class passengers on weekday services in autumn last year.
The average proportion of passengers carried in excess of capacity on peak services in major cities was 3.8%.
Lianna Etkind, of the Campaign for Better Transport, said: "The latest statistics show that overcrowding continues to make passengers' lives a misery.
"People are rightly angry that they pay more in fares year after year, but never get a seat, and have to stand crammed into someone else's armpit.
"With such high levels of overcrowding, the Government cannot expect people to pay for yet another fares hike in January."
Anthony Smith, chief executive of passenger watchdog Transport Focus, said: "Continuing to invest in new trains, better frequency, track capacity and improved signalling will ultimately give passengers a better chance of getting a seat or at least stand in some comfort.
"In return for continuing fare rises passengers expect continued investment and improvement."
:: Here are the most overcrowded trains in England and Wales (figures in brackets represent their most crowded point):
1. 7.16am East Grinstead to London Bridge (640 capacity and 1,366 passengers carried)
2. 7.55am Cambridge to London King's Cross (202 capacity and 426 passengers carried)
3. 5.08pm Sutton to St Albans City (391 capacity and 758 passengers carried)
4. 6.57am Brighton to Bedford (630 capacity and 1,215 passengers carried)
5. 4pm Manchester Airport to Edinburgh (191 capacity and 357 passengers carried)
6. 7.27am Reigate to London Bridge (669 capacity and 1,233 passengers carried)
7. 5.18pm London Paddington to Oxford (242 capacity and 445 passengers carried)
8. 4.22am Glasgow Central to Manchester Airport (191 capacity and 344 passengers carried)
9. 4.26pm Bedford to Brighton (372 capacity and 669 passengers carried)
10. 6.13pm London Euston to Birmingham New Street (412 capacity and 729 passengers carried)
Jacqueline Starr, managing director of customer experience at the Rail Delivery Group, which represents train operators and Network Rail, said: "We understand passengers' frustration when they can't get a seat, which is why rail companies are working together to invest and make journeys better with thousands of new carriages and 6,400 extra train services a week by 2021.
"We will continue to work with governments to increase seats on key routes to boost communities, businesses and the economy."