A woman with cerebral palsy was left in tears after being publicly removed from a ride at Alton Towers.
"Adrenaline junkie" Hannah and her sister Becky Cheetham visited the resort on Monday to celebrate a birthday.
In a Facebook post addressed to the park, the sisters wrote they had an unforgettable day "for all the wrong reasons."
Alton Towers said it was "deeply sorry" for the incident.
Ms Cheetham, who uses a wheelchair, has visited the park every year and has previously gone on every ride she wanted.
When the sisters, from Greater Manchester, went to go on the Smiler ride, a park worker shouted "she can't walk" to another co-worker, "embarrassing" them by shouting about it "across the ride for a crowd of people to hear".
They arrived at another ride, Rita, where workers watched as Ms Cheetham carried her sister to the ride.
Once strapped in, they were then told they were not allowed on the ride due to health and safety.
Ms Cheetham said she was in tears after the workers "embarrassed" her by "publicly" removing her sister from the ride, leaving her "angry and fed up due to the ignorance of your staff".
The sisters went to a further ride, Duel, as it has disability access, but were later told by a member of staff the disabled access was not there anymore.
Ms Cheetham said at that point they left the park, having spent £40 each on tickets to go on two rides.
A petition started by the pair online calling for disability awareness training for public-facing staff members, has more than 27,000 signatures.
Ms Cheetham said the attitude of staff was "disgraceful" and not one person had spoken directly or apologised to her sister.
Kate McBirnie, from Alton Towers, said the experiences fell "well below the high expectations we have for our employees".
She added: "At Alton Towers Resort, we pride ourselves on being an inclusive resort and we really value the feedback that Hannah and Becky have sent to us.
"We have certainly listened and we want to do better - particularly in the area of staff training and the way we communicate ride restrictions to guests with disabilities."
Alton Towers' website says it "strives" to make sure attractions are "easily accessible to all our guests", and offers an online ride-by-ride guide.