Passenger levels on railway branch lines are being grossly underestimated in documents given to firms bidding for a franchise, the BBC has learnt.
Bidders for the Greater Western franchise have been told Cornwall's Lelant Saltings station deals with several hundred passengers a year.
However, sources have told the BBC the St Ives' line station actually deals with several hundred thousand.
The deadline for the 15-year franchise bids expired earlier this week.
Industry insiders said the Lelant Saltings was a unique case.
Neil Gallacher, BBC South West Business Correspondent, said: "Industry insiders say Lelant Saltings is unique because of the particular 'rover' ticket type used by the overwhelming majority of people who get on there.
"They say its popularity among passengers was widely understood."
The line runs between London, the west of England, south Wales and parts of the Midlands.
Current operator First Great Western, which was awarded the franchise in 2005, said it did not want to take up the option to extend its current contract beyond March 2013.
Several large UK and European rail firms are said to be interested in taking over the franchise.