They claim some of the late night trains from CMK to Euston had been cancelled at the last minute without reason after the concert ended.
That left thousands of fans trying to cram into a single train, the 11.45pm London Northwestern.
Passenger Hattie Daniels has claimed people were screaming, fainting and suffered bruising as a result of being crushed but unable to escape.
She said: “The crowd surged into the carriage and we were completely pinned in the space between the two seating areas.
“More and more passengers tried to force their way in, out of clear desperation not to be left stranded by the lack of further transport. Members of our party were lifted so their feet were no longer touching the floor, while others felt the weight of holding them up.
“We were all begging, screaming, crying and shouting for them to stop pushing us and telling them people were getting hurt.”
When the train stopped at Bletchley, the situation became even worse as more fans tried to board.
"We were trying to stop them coming in. There was just no room at all - people were even crammed into the toilets. But they still squeezed in. By this time the train was so crammed that the doors couldn’t even shut,” claimed Hattie.
She had a degree in criminology and studied the Hillsborough disaster as part of her university course.
"It reminded me of Hillsborough in that it showed how dangerous a crush can be. I kept worrying that someone would be seriously injured or even killed because it was so bad.”
The nightmare journey took an hour and a half. People with water passed the bottles around to those who were fainting or struggling to breathe.
But at no stage did Hattie see a London Northwestern office or a member of British Transport police on board, she claimed.
But by the time the train arrived at Euston, many passengers were in a bad way, said Hattie.
"People were just laying on the platform, unable to move or feeling faint. Many missed their connections and had no idea who they’d get home.”
Afterwards when Hattie tried to complain, she was told the number of people on the train was unexpected and “unprecedented”.
"It was a beyond poor excuse given the 30,000 seat MCR gig had been delayed by two years due to Covid, and there had been an MCR show earlier that week at the same stadium,” she said.
A London Northwestern Railway spokesperson told the Citizen: “We are sorry to customers at Milton Keynes whose train was uncomfortably busy on Saturday evening following the short-notice cancellation of another service.
“In order to ensure everyone was able to get home we arranged for a special late-night train to collect passengers who were unable to board.”
A spokesman for the transport police said: “British Transport Police were called to Bletchley station at 12.23am on Sunday 22 May following reports of overcrowding on a train to London.
“Officers attended and assisted with directing passengers to another service.”