The shocking allegations have been made by McLachlan's former The Rocky Horror Show musical co-stars, and reportedly took place on and off stage during his 2014 performance as Dr Frank-N-Furter, the ABC and Fairfax report in a joint investigation.
Actresses Christie Whelan Browne, Erika Heynatz and Angela Scundi have all alleged that over the course of the performance season, the silver and gold Logie winner performed a range of indecent acts.
These indecent acts include McLachlan allegedly exposing himself to one member of the cast, kissing another without permission and pulling one cast member's underwear down and kissing her backside during a performance.
Angela Scundi said, 'There were multiple incidences where he would try and put his hands up women's costumes or down their pants. And it was always when they could be seen by the audience and he couldn't.'
Ms Scundi also alleges that when she confronted McLachlan over his inappropriate behaviour, 'he turned.'
'I haven't felt that terrified ever in my life,' she said.
Another alleged victim, Erika Heynatz, told Fairfax that McLachlan was a 'really calculated and very manipulative predator.'
She said, 'He's a larrikin, up for a laugh and certainly, when we all first met him, that's indeed how he came across.
'There is another side to this man that he has very, very craftily and cleverly disguised from people for so long.
'It's like this split personality. The other personality is this sinister, predatory behaviour.'
The alleged victims have filed separate police reports with Victoria Police.
McLachlan has denied all allegations, calling them 'simple inventions.'
In a statement released to ABC, the 52-year-old actor wrote: 'Frankly, they seem to be simple inventions, perhaps made for financial reasons, perhaps to gain notoriety. In either event, they are to the best of my knowledge utterly and entirely false.'