Former adviser Stephanie Solange Calo lodged a criminal complaint against Romero on Monday, alleging that he exposed his penis to her and tried to force her to practice oral sex on him during a party in which Romero allegedly locked her in a bathroom.
"Romero grabs me, locks me inside the bathroom with him, he stops me from leaving. He pulls down his pants, takes out his member and starts to ask me to practice oral sex on him", she said in a statement.
Calo explained that she felt "desperate" during the alleged attack.
"I refused several times and I demanded that he let me out. I even had to promise him that we would do it the next day so he would let me out. I banged on the door and walls so someone would let me out. Nobody helped me", she added.
In 2017, Romero was elected provincial senator for the Citizens United, the party which former president Cristina Fernández de Kirchner led on a national level during last year's mid-term elections. He is a former Florencio Varela city councillor.
"To our female members, you are believed and accompanied. We want to make the personal the political, to shed light on injustices and to build a better organisation that gives answers to new social demands", the organisation said in an official statement.
"We will no longer tolerate the many barriers in place to measure the behavior of our colleagues. It does not matter how important they are or what their responsibilities are", it added.