CCTV images have been released appearing to show Jeremy Corbyn walking past empty unreserved train seats before he was filmed sitting on the floor complaining about “ram-packed” carriages.
The Labour leader was travelling on the three-hour 11am Virgin Trains service from London King’s Cross to Newcastle on August 11.
A video emerged last week which showed him sitting on the floor and describing a lack of seats as “a problem that many passengers face every day”.
He then called for public ownership of the railways.
But Virgin Trains released CCTV images which appear to show Mr Corbyn and his team walking past empty unreserved and reserved seats at 11.07am.
He recorded his video message on the floor around 30 minutes into the journey before finding an unreserved seat at 11.43am with the help of the on board staff, Virgin Trains said.
Billionaire Sir Richard Branson, who co-owns the train operator with Stagecoach, posted a link to the CCTV images on his Twitter account and wrote that Mr Corbyn “walked past empty unreserved seats”.
A spokesman for Virgin Trains said: “We have to take issue with the idea that Mr Corbyn wasn’t able to be seated on the service, as this clearly wasn’t the case.”
Mr Corbyn was on his way to debate with Owen Smith in a Labour leadership hustings in Gateshead.
A spokesman for his campaign said: “When Jeremy boarded the train he was unable to find unreserved seats, so he sat with other passengers in the corridor who were also unable to find a seat.
“Later in the journey, seats became available after a family were upgraded to first class, and Jeremy and the team he was travelling with were offered the seats by a very helpful member of staff.
“Passengers across Britain will have been in similar situations on overcrowded, expensive trains. That is why our policy to bring the trains back into public ownership, as part of a plan to rebuild and transform Britain, is so popular with passengers and rail workers.”
Virgin Trains confirmed that two passengers were moved to first class so that Mr Corbyn could sit next to his aide.
Keren Harrison, 45, was travelling on the train and struck up a conversation with the Labour leader when she saw him sitting on the floor.
Mrs Harrison, who is not a supporter of the party, told the Press Association: “I spoke to him and then the staff came over and said ‘we’ll try and find you some seats, sir’ - I don’t know if they would have done it for any other passenger - and off they went before coming back and offering him a seat in first class.
“He declined them and I thought he was obviously a man of morals and doesn’t want to sit in first class.
“They then came up and said they had managed to find him some seats and I got the impression they had moved some people around.”
During the video in which Mr Corbyn is sitting on the floor, he said: “This is a problem that many passengers face every day on the trains - commuters and long-distance travellers.
“Today this train is completely ram-packed. The staff on the train are absolutely brilliant, working really hard to help everybody.
“The reality is there’s not enough trains - we need more of them - and they’re also incredibly expensive.
“Isn’t that a good case for public ownership?”
Charles B Anthony, who wrote a story about the video for the Guardian, posted a number of messages on social media in response to the Virgin statement.
He said: “Corbyn wants to renationalise their business. You do the math.”
Mr Anthony also published a series of images of the Labour leader chatting to other passengers forced to sit on the floor and footage of him walking through a carriage where the seats were occupied.
A Virgin Trains spokesman said: “We’d encourage Jeremy to book ahead next time he travels with us, both to reserve a seat and to ensure he gets our lowest fares, and we look forward to welcoming him on board again.”
TSSA union general secretary Manuel Cortes accused Virgin of being “disingenuous” and said Mr Corbyn had “highlighted this daily travel blight which means people sit on floors on trains every day because of overcrowding”.
Mr Smith appeared to make reference to the issue in a Twitter post which read: “My campaign remains on track. Proud to be genuinely standing up for ordinary people.”