The apology comes four months after a joint parliamentary committee found that bullying is rife in the ranks of the regulator.

The cross-party committee urged WorkCover to make a public apology to staff including Wayne Butler, an employee it was forced to reinstate after it sacked him for dubious reasons. The committee said this was important to help the organisation rebuild trust with staff.

A letter by Vivek Bhatia, chief executive officer of the WorkCover Safety, Return to Work and Support dated on Wednesday apologised for the way Mr Butler was treated during an investigation and for his dismissal. WorkCover accepts that he was exonerated and completely cleared of all allegations.

"This is an unconditional apology, made without any qualifications or reservations. I regret the way in which you were treated during the investigation and your dismissal and I acknowledge that you and your family did go through a difficult and distressing time. I would also like to extend my apology to your family as well," the letter said.

"The STWS Executive Team and I, sincerely apologise for all statements made during the inquiry hearings which may have inferred that WorkCover held other evidence if misconduct by yourself. This is not the case at all.

"I confirm there are no matters to your conduct other than the allegations made against you in 2012. All of those 2012 allegations were not sustained even partially in a court of law, whose decision we accept without reservation."

Deputy President of the NSW Industrial Relations Commission Rodney Harrison described an investigation WorkCover conducted into Mr Butler as little more than a "witch-hunt" and characteristic of "institutional bullying".

Mr Butler had spent 12 years in WorkCover's Safety, Return to Work and Support Division until being sacked in November 2012 following an investigation Mr Harrison denounced in June last year as "deplorable".

The committee also recommended new anti-bullying laws for all workers in NSW in a report that was damning of WorkCover. It also called for independent oversight of the agency, which has responsibility for regulating workplace safety and providing workers compensation.

Greens MP and Industrial relations spokesperson David Shoebridge said the government apology comes just 48 hours before WorkCover is required to make its submission to the Parliamentary Inquiry into bullying.

"Without this continuing Parliamentary pressure it is pretty obvious that WorkCover would not have apologised," he said.

"This apology is far too late, but I welcome the fact that it is unconditional and has finally been delivered.

"Mr Butler, like every employee in NSW, deserves to be treated with far more respect than he received at the hands of WorkCover."