The 0822 Oxford to London train is the most overcrowded in southern England
A rail service from Oxford to London Paddington carries almost 60% more passengers than it should, government figures have shown.
The 0822 First Great Western (FGW) service was named in figures released by the Department for Transport (DfT) under the Freedom of Information Act.
The turbo commuter train only has three carriages and is the most overcrowded service through southern England.
FGW said it had submitted proposals to the DfT to lease additional carriages.
The figures also showed two South West Trains services between Portsmouth and London Waterloo were overcrowded.
The 1639 service from London Waterloo and the 0615 direct train from Portsmouth both carry 40% more people than they should, according to the figures.
The Portsmouth trains are often so crowded that the guard cannot pass through the carriages to check tickets, BBC South's Transport Correspondent, Paul Clifton, said.
The statistics are from 2007, the most recent full year of figures, he added.
South West Trains (SWT) said it planned to add three extra carriages to the 1639 from London Waterloo next month.
SWT also said it had submitted proposals to the DfT to lease additional carriages to ease overcrowding.