A woman said she was left having seizures on the floor of a hospital room for more than an hour because no bed could be found for her.
Jodie Lee said staff at the Royal Liverpool Hospital did not understand her mental health needs.
"I felt like a dog," said Ms Lee, who claimed she was lying in her pyjamas with just a blanket for a pillow.
A hospital spokesman said Ms Lee left the hospital before she could receive specialist mental health assessment.
Ms Lee, from Liverpool, referred herself to the hospital on Friday when she started experiencing symptoms associated with Functional Neurological Disorder (FND).
FND sees patients suffer neurological symptoms which are not caused by a disease of the nervous system.
She told the BBC's Victoria Derbyshire programme she was continuing to have seizures and "all the nurses done was carry out observations and leave me on the floor".
Her family asked for her to be given a bed but she said they were told she "wasn't eligible for a bed as I was waiting for the [mental health] crisis team".
A hospital spokesman said Ms Lee was "triaged by the mental health team within 30 minutes of arrival and was then awaiting assessment by the specialist mental health team".
He said Ms Lee was in a "specially designed mental health suite in A&E and had family members with her" and said the room was "designed not to be a clinical area and as such has comfy chairs but not a bed".
The spokesman added although Ms Lee did not need a bed on medical grounds "our staff recognised the discomfort she was experiencing, and were in the process of making a bed available".
He said she left the department before a bed became available and prior to receiving the mental health assessment.