Jo Tarnawsky alleged she was ousted from her position after raising allegations of bullying.
She said while Mr Marles was not a part of the bullying, he had told her to look for a different job after raising concerns about her treatment in the office.
Jo Tarnawsky held a press conference at Parliament House in Canberra on Thursday. (Mick Tsikas/AAP PHOTOS)
"I have been plagued with nightmares, flashbacks, symptoms of depression and anxiety, panic attacks and suicidal thoughts," she told reporters in Canberra on Thursday.
"(This) was a job that I dreamed of having since I first visited Parliament House as a child. Now I am the most senior female chief of staff on the hill, and my workplace is not safe."
Mr Marles said he was satisfied the ministerial code of conduct was not breached, and that he was grateful for the service of his former employee.
"She is a person who is completely committed to social justice in this country and I very much admire her ... I feel very sad that events have got to where they have. It is obviously very difficult," he told parliament.
"The way in which I have tried to manage this, I have done so with Jo's welfare in mind at every moment, as I would try to manage things on that basis for all of my staff.
"This matter is now in the hands of lawyers, of course that is absolutely Jo's right, but it does mean that it is difficult for me to say anything more on this."
Richard Marles said Prime Minister Anthony Albanese had been told about the allegations. (Mick Tsikas/AAP PHOTOS)
Mr Marles said Prime Minister Anthony Albanese had been told about the allegations.
"I have been working with the prime minister's office for months in respect of this matter," he said.
Ms Tarnawsky said she had been "broken" by the alleged bullying that had occurred in Mr Marles's office.
While a legal claim had yet to be lodged, she said she wanted accountability over the situation.
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