The controversial former boss of the Health Services Union Michael Williamson has been charged with a total of 20 offences.

Five of those charges relate to recruiting five other people to commit criminal acts by hindering a police investigation.

One of those people is understood to be his son Chris, a former employee of the Health Services Union.

Outside Maroubra police station in Sydney's east, the head of the Fraud Squad, Superintendent Colin Dyson, said that Mr Williamson is alleged to have hindered the police when he and his son removed a bag of documents from the union's Pitt Street headquarters while police were executing a search warrant at the premises in May this year.