A wheelchair user was refused space on a bus because a pushchair was on board, days after the Supreme Court ruled on the issue.
Kirsty Shepherd, from Wakefield, West Yorkshire, said the Arriva driver told her she could not get on, even though there was enough room.
It came five days after the Supreme Court said bus drivers must be more accommodating to wheelchair users.
Arriva Buses said it was investigating "as a matter of urgency".
Ms Shepherd said the woman with the pushchair on the Rothwell to Wakefield bus was happy to move, but the driver still would not let her on.
In the case that went to the Supreme Court, wheelchair user Doug Paulley took action against First Bus after he was refused entry to a bus in 2012 when a mother with a pushchair would not move.
The bus had a sign saying: "Please give up this space if needed for a wheelchair user."
The court found the company should do more to persuade non-wheelchair users to move from wheelchair spaces, but did not have the legal power to remove them.
'Just not fair'
Ms Shepherd said the Arriva driver told the passengers to get off, saying it was her fault the journey could not go on.
"He leant forward and said 'I can't let you on love, I've got a pushchair on'," she said.
"I said 'well please ask her to move'. He said 'I can't do that'.
The woman with the pushchair moved of her own accord but the driver still would not let Ms Shepherd on.
"The people on the bus started shouting saying 'just get the next bus, we've got homes to get to'," she said.
Ms Shepherd added that she spoke to the bus driver's manager, but he was still not willing to let her on board.
The service was then terminated at a bus stop and everyone got off, before the bus was put back into service some time later.
"He let the passengers get off and have a go at me... it was just not fair."
Arriva said: "Our customer service team have had extensive conversations with Ms Shepherd about the incident and we are investigating this as a matter of urgency.
"We are in the process of downloading the CCTV footage and speaking to those involved.
"We have promised to conclude this investigation swiftly."
Commenting on the case, Mr Paulley said he could not see why Ms Shepherd had been denied a bus journey.
He said: "On her bus there was a buggy space, so there were two separate spaces. When that lady [with the pushchair] moved into the buggy space that space was free and available, so I don't know why the driver didn't let her on."
He said he thought the Supreme Court ruling had gone far enough to help wheelchair users.
"I think some people would have liked it if it was more concrete," he said. "But there are always exceptional circumstances, so there has got to be some flexibility.
"I think also the Supreme Court justices went quite a long way to reach the decision that they did, and it has really raised awareness."