Hundreds of people may have been exposed to HIV and other infectious diseases after they received treatment at a Macquarie Street hair replacement clinic.

An investigation by public health authorities has found evidence of poor infection control practices, including problems with the cleaning and sterilisation of surgical instruments and equipment at the clinic run by Angela Katarina Campbell in Suit 23 at 193 Macquarie Street.

The South Eastern Sydney Local Health District revealed on Wednesday afternoon that Dr Campbell's medical registration was cancelled in late February after an investigation by the Medical Council of NSW.

But the district only became aware of the potential public health threat posed by the clinic months later, when neighbours in her building reported concerns about how medical waste was being stored.