Financial advisory firm EY has strongly dismissed explosive claims from a Labor senator that accused the company of gross worker exploitation, humiliation and inappropriate behaviour towards employees.

Senator Deborah O'Neill excoriated the culture and governance at EY on Tuesday night, using parliamentary privilege to air allegations of illicit drug-taking and alcohol abuse at the workplace as well as sexual harassment, assault and fraud over a number of years.

Senator Deborah O'Neill has used parliamentary privilege to excoriate EY's culture and governance. Credit:Eamon Gallagher

"I have been informed of claims of partners being under the influence of alcohol, behaving inappropriately and sometimes undermining, humiliating and ostracising officers in the presence of other employees while off premises, as well as officers coming to work under the influence of illicit drugs in a desperate attempt to fiercely compete for that sales credit," Senator O'Neill said.

In an emailed statement to The Sydney Morning Herald and The Age, an EY spokeswoman rejected the senator's claims. "There are so many factual inaccuracies in the commentary," she said.