ABC journalist Ashleigh Raper claims NSW Labor leader Luke Foley put his hand through a gap in the back of her dress, inside her underpants and "rested his hand" on her buttocks, in a statement released on Thursday.
Last week Foley called her and apologised, Raper wrote in a statement released on Thursday afternoon by the ABC.
"This is a position I never wanted to be in and a statement I never intended to make," Raper said.
It was time for her "voice to be heard", she said, because the public debate about the alleged incident had escalated.
Foley has previously denied harassing a then unnamed ABC journalist, after he was accused in parliament by corrections minister David Elliott of harassing a female reporter after having “a little bit too much to drink at a party”.
"In November 2016 I attended an official Christmas function at New South Wales Parliament House for state political reporters, politicians and their staff," Raper said.
"This is what happened on that night."
Raper said the party moved from NSW parliament house to a bar at Martin Place.
"Later in the evening, Luke Foley approached a group of people, including me, to say goodnight. He stood next to me. He put his hand through a gap in the back of my dress and inside my underpants. He rested his hand on my buttocks.
"I completely froze."
Raper said the incident was witnessed by Sean Nicholls, who was then the state political editor at The Sydney Morning Herald and is now an ABC journalist.
"As shaken as I was, I decided not to take any action and asked Sean to keep the events in the strictest confidence," Raper said. "He has honoured that."
Raper said she chose not to make a complaint for a "number of reasons".
"It is clear to me that a woman who is the subject of such behaviour is often the person who suffers once a complaint is made," she said. "I cherished my position as a state political reporter and feared that would be lost.
"I also feared the negative impact the publicity could have on me personally and on my young family."
But that impact was now "being felt profoundly", she said.
"Last Sunday (4 November) Luke Foley called me on my mobile phone and we had a conversation that lasted 19 minutes," Raper said.
"He said he was sorry and that he was full of remorse for his behaviour towards me at the Press Gallery Christmas function in November 2016.
"He told me that he had wanted to talk to me about that night on many occasions over the past two years because, while he was drunk and couldn’t remember all the details of the night, he knew he did something to offend me."
Raper said Foley apologised again and told her, “I’m not a philanderer, I’m not a groper, I’m just a drunk idiot”.
Raper said Foley told her he would resign as leader of the NSW Labor Party on Monday or Wednesday of this week, but not on Tuesday as he didn't want to be "accused of burying the story" to coincide with the Melbourne Cup.
He called on the Tuesday, she said, to repeat his apology and notify her that he'd received legal advice not to resign as opposition leader.
"He indicated he intended to follow that advice," Raper said.
There were three things she said she wants to come from the decision to go public with this information.
"First, women should be able to go about their professional lives and socialise without being subject to this sort of behaviour," she wrote.
"And I want it to stop."
Secondly, she wants situations like hers not to be "discussed in parliament for the sake of political point scoring".
"Third, I want to get on with my life."
The allegations were aired without Raper's permission by counter-terrorism and corrections minister David Elliott in state parliament last month.
Federal Liberal senator Eric Abetz then put written questions to the federal minister for communications about the allegations during Senate Estimates, and ABC management undertook to investigate.
Abetz had given the public broadcaster until November 24 to respond. If they didn't answer his questions he threatened to take steps in the federal Senate to force a response by the end of the federal parliamentary sitting year on December 6.
A NSW Labor source told BuzzFeed News that Foley can no longer remain as leader of the party and expects he will stand down within hours.
It's understood deputy leader Michael Daley will be his replacement and lead the party to the March state election.
Federal Labor leader Bill Shorten refused to comment on the serious allegations because he hadn't read the statement. "I'm unable to assist you, it's an issue for Mr Foley," Shorten said at a press conference on Thursday afternoon.
"I said it’s a serious matter and it’s a fair question, but it’s just broken while I’ve been here, so I’ll go away and get acquainted on the facts."
BuzzFeed News has contacted Foley for comment.
Elliott's office told BuzzFeed News he will not be commenting on the issue.
UPDATE
Labor member for the Blue Mountains, Trish Doyle, has called on Foley to resign or face a leadership spill.
In a statement she said: "The allegations against Luke Foley are serious and they are unacceptable.
"I am concerned that this issue has drawn out and caused such distress and anguish for the journalist at the centre of it.
"In my view, Mr Foley’s position is untenable and he must resign today. Bad behaviour is bad behaviour, whoever does it.
"In the event that he refuses to resign, I will call for a spill of the NSW Labor leadership to resolve this issue."