Williamson jailed for at least five years

Former Health Services Union boss Michael Williamson has been jailed for at least five years for systematically defrauding the union of almost $1 million and hindering a police investigation.

Williamson showed no emotion as he was sentenced to a maximum seven-and-a-half years at Sydney's District Court on Friday.

In a damning judgement, Judge David Frearson said Williamson oversaw a "parasitic plundering of the union funds for pure greed".

The frauds were calculated, brazen and arrogant and involved an "extreme" breach of trust.

"(It was) a reprehensible betrayal of the union and all its members," he said.