An investigation is underway after a cancer patient had the wrong side of his bowel removed at Sydney's troubled Northern Beaches Hospital last week.

Key points: The botched colorectal surgery was due to a mistake by a private pathology provider

The botched colorectal surgery was due to a mistake by a private pathology provider The patient has since undergone corrective surgery at the hospital

The patient has since undergone corrective surgery at the hospital A parliamentary inquiry into the seven-month-old facility is due to start in August

The mistake was the result of a privately contracted laboratory mishandling the patient's pathology results.

Opposition Health spokesperson Walt Secord said the botched colorectal surgery proves an inquiry into the facility is necessary.

"This vindicates the Opposition pushing for an inquiry into the Northern Beaches Hospital ... the inquiry will begin taking evidence next month but again the Health Minister has a responsibility to make the results of the report into this incident public," he said.

"But again another day, another incident at the Northern Beaches Hospital."

The hospital in Frenchs Forest has been marred by controversy since opening last November with the head nurse, head of anaesthetics and the hospital's chief executive all resigning over the past seven months.

In an email to management, a senior anaesthetists who also resigned said the facility "fails completely in its primary objective of patient safety".

Health minister Brad Hazzard said an investigation into the surgery was already underway.

"In such situations there are investigative processes and those must proceed to their conclusion before any further comment can be made," he said.

"The patient's privacy must also be respected."

The patient has since returned to the hospital for corrective surgery.

The hospital's operator Healthscope said the patient and their family were getting ongoing care and treatment.

A parliamentary inquiry into the operation and management of the Northern Beaches Hospital will begin in August and former staff are expected to be called to give evidence.

In successfully moving for the inquiry, Mr Secord told parliament the hospital had "lurched from crisis to crisis" since opening.