The Association of Train Companies (ATOC) has strongly denied Union claims that private operators have no idea about passenger numbers during peak times, arguing that there are systems in place to collect the data.
Union leaders at the TSSA hit out at the rail companies after the Office of Rail and Regulation told a Commons Transport Select Committee that train operators had no firm figures detailing the number of passengers commuting during peak times.
Anna Walker, chair of the ORR, told the committee: "There are estimates but that is all they are. One of the things that is really crucial on the question of crowding is the need for investment in ticketing machines so that we have real information in the way we do not at the moment about numbers on each service.
"We do not have that and we need more electronic ticketing services to get that."
TSSA union general secretary Manuel Cortes has said that he is now writing to the transport secretary, Justine Greening, urging her to instruct the companies to gather more data.
"We have a ridiculous situation for passengers in the 21st century," said Cortes.
"They have to travel in cattle truck conditions with no limits on overcrowding while cattle travel under regulations which restrict overcrowding."
However, a senior spokesperson for ATOC dismissed the claims as "nonsense" and insisted that rail operators already had systems in place to collect data on passenger numbers, which aids timetabling and fleet distribution planning.
ATOC has said that the train companies have the information, they just aren't sharing it all with the ORR.
"All new trains have automatic passenger counts. These work using weighing equipment within the fleet, which feeds information on how many passengers are on the train into a database. This information is then downloaded and analysed on a weekly basis," said the ATOC spokesperson.
"They will use this information to calculate and predict flows on passenger routes. If an operator has older trains they carry out manual counts or use data on ticket sales," she added.
However, ATOC did say that although tickets sales were used as an indicator to predict timetables and passenger flows, this has been made more difficult by the introduction of pay-as-you-go technology, such as the Oyster card in London.
"They also use data off the back of how many tickets have been bought. However, in London for instance, customers may use the Oyster card, which if being used as pay-as-you-go means that you can't predict data in the same way that you can when season tickets are bought," said ATOC's spokesperson.
Greening unveiled extensive plans last month to deliver £3.5 billion worth of efficiency savings across the UK's railways by 2019.
In a report, entitled 'Reforming our Railways: Putting the Customer First', the transport secretary confirmed support for a nationwide rollout of smart cards, as well as increased use of new technology channels, such as Twitter, that could be used to improve passenger access to reliable information flows about disruption to service.