Richard Branson having a "pop" at Jeremy Corbyn over train seating shows the establishment is "absolutely petrified", the Labour leader's campaign director has said.
Sam Tarry said the "spat" with Sir Richard, who co-owns Virgin Trains with Stagecoach, was rooted in the billionaire being "upset" about Mr Corbyn's plans to renationalise the railways.
Mr Tarry, also a political officer with the TSSA union, made the remarks during an east London rally for Mr Corbyn hours after CCTV images were released by Virgin Trains.
The train operator's images appeared to show Mr Corbyn walking past empty unreserved train seats before he was filmed sitting on the floor complaining about "ram-packed" carriages.
The MP 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.
Businessman Sir Richard 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."
But Mr Tarry told an event in support of Mr Corbyn's leadership re-election bid: "Some of you might have seen on social media today there's been a little bit of a spat.
"Richard Branson has decided he's very upset about our not particularly radical plans to renationalise our railways so he's having a little pop at us.
"I'd just say that's very, very indicative - the establishment is absolutely petrified about what this campaign is about, what this movement is about."
Mr Corbyn was on his way to debate with Owen Smith in a Labour leadership hustings in Gateshead when pictured on the train.
His campaign team said he was unable to find unreserved seats for his group, which included aide Emma Rees and his wife Laura Alvarez, so he sat with other passengers in the corridor who were also unable to secure a seat.
Mr Corbyn's campaign spokesman also said: "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."
In response to Mr Corbyn's statement, Virgin said: "We're a bit puzzled why Jeremy couldn't find unreserved seats when he boarded the train - they're right next to him as the photo shows."
Mr Corbyn's campaign spokesman said there were coats and bags on the seats which indicated people were sat there.
The spokesman also said they were looking into whether Virgin Trains breached Information Commissioner's Office data protection guidelines by releasing the CCTV.
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."
TSSA 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".