A Sydney pub admits it "screwed up" after security staff refused entry to a young woman with cerebral palsy, believing she was drunk.

The Marlborough Hotel, in Newtown, apologised "unreservedly" on its Facebook page today after the patron, who was out to celebrate her 21st birthday with friends, was turned away on Sunday morning.

The pub began investigating the incident after Liane Gorham posted a public message claiming it was her friend's daughter who was "belittled and laughed at".

"She suffers from cerebral palsy. Disgraceful and discriminating behaviour by your door staff," Ms Gorham wrote.

"Shameful!"

'She just wanted to have a great night'

Other friends also took to the pub's page to complain about the incident.

Ruth Disher, who also said she was a friend of the woman involved, said it was "disgusting", while Anne Marie questioned the training of the venue's security.

"Surely your security guards have been taught that there are other ways to tell if a person is intoxicated other than the way someone walks," she said.

"You have insulted and upset this young woman, she lives with this disability everyday, she just wanted to have a great night with her friends for her 21st and your pathetic security guards go and do that."

The Marlborough posted a public apology admitting it had "screwed up" after investigating the incident.

"We apologise to the young lady, her friends and family. Unreservedly," the post said.

"We apologise for the humiliation and distress that we have caused.

"We are committed to building awareness of this issue with our entire team through intensive anti-discrimination training."

The ABC understands the security staff involved have been fired.

Staff deserve ridicule, Minister says

NSW Disability Services Minister Ray Williams said he struggled to come to terms with the "appalling" behaviour of the staff and "equally abhorrent" comments that were made about the young woman.

He said the incident flew in the face of the National Disability Insurance Scheme's fundamental objectives to create a more inclusive society.

"I can only hope everyone can take a lesson out of what has happened and make sure they are respectful to all people, especially some of the most vulnerable people in NSW, those people with disability," Mr Williams said.

The hotel was understandably the subject of a boycott, he added.

"Australia is the land of the supporter of the underdog. I certainly think they always show great respect and great support for people with disability," Mr Williams said.

"Sadly it's been lacking in this regard by these staff members and they deserve the ridicule that is now being heaped upon them."

Australian Disability Discrimination Commissioner Alastair McEwin said: "Sadly, I have seen many similar reports of security staff assuming a person with disability is intoxicated, when that is not the case."

"Security and other hospitality staff must be aware of the diversity of disability — we come in many different forms."

The Marlborough Hotel was contacted for comment.