A prominent Silicon Valley investor has resigned following allegations of sexual harassment, and just hours before a fresh allegation surfaced, this time of sexual assault.

On Monday, Dave McClure resigned as general partner of 500 Startups, the seed investment group he co-founded in 2010, after several women accused him of inappropriate behavior. He had already stepped down as chief executive of the investment group following the allegations and published a blog post apologizing for being “inappropriate”.

The blog posted prompted entrepreneur Cheryl Sew Hoy to come forward with an even more serious allegation: that McClure sexually assaulted her three years ago.

“I’m now ready to tell my account of what Dave McClure inflicted on me three years ago, in my own apartment. It’s not just inappropriate, it’s assault,” she wrote in a blog post on her website.

McClure did not immediately respond to repeated requests for comment.

His resignation comes one week after well-connected venture capitalist Justin Caldbeck admitted to sexually harassing female entrepreneurs and stepped down in the face of numerous public accusations. A former Uber engineer’s account of harassment and discrimination also went viral in February, sparking widespread outrage about sexism in Silicon Valley.

McClure’s departure from 500 Startups was announced by co-founder Christine Tsai in an email sent to the company’s investors on Monday. The email stated that 500 Startups had received several harassment allegations against McClure, investigated and “found his behavior to have been unacceptable”. The email added that 500 Startups “cannot be certain there won’t be future reports”.

One of the women who came forward was entrepreneur Sarah Kunst, who was one of more than two dozen women who spoke to the New York Times about sexual harassment in Silicon Valley. Kunst alleges that McClure sent her sexually suggestive Facebook messages while she was discussing a possible job at 500 Startups. “I was getting confused figuring out whether to hire you or hit on you,” said McClure in one message.

The day after the article was published, McClure wrote a blog post apologizing for his actions, titled “I’m a creep. I’m sorry.”

“I made advances towards multiple women in work-related situations, where it was clearly inappropriate,” he said. “I put people in compromising and inappropriate situations, and I selfishly took advantage of those situations where I should have known better. My behavior was inexcusable and wrong.”

When Sew Hoy saw McClure being praised for his honesty and bravery, she said, she decided to speak up.

“People were saying ‘it’s just Dave being Dave’,” Sew Hoy told the Guardian. “Then I realized I had the power to change the narrative not just for myself but for a greater cause: other women.”

“I felt like this story – after Ellen Pao and Susan Fowler – could be the tipping point for a whole cultural shift in the industry.”

In her blogpost, Sew Hoy said McClure assaulted her in her own apartment three years ago. Sew Hoy’s startup ReclipIt had been funded by 500 Startups, and McClure had flown to Malaysia to meet investors in her new venture, she wrote.

McClure and several others came to Sew Hoy’s apartment to brainstorm, but what “started out to be an innocent night of just jamming and hanging out at my new apartment turned into a nightmare episode that has been haunting me for the past three years”, she said.

According to Sew Hoy’s account, McClure continued to pour scotch into her glass before she had finished drinking, and eventually everyone left except McClure. She asked him if he wanted to leave, and he said no, at which point she offered to let him stay in a guest room, Sew Hoy wrote.

“I went into my own bedroom but Dave followed me there, and that’s when he first propositioned to sleep with me. I said no. I reminded Dave that he knew my then-boyfriend and that we’d just talked about him earlier that night,” she wrote.

She said that after she led him to the door to get him to leave, “he pushed himself onto me to the point where I was backed into a corner, made contact to kiss me, and said something along the lines of ‘Just one night, please just this one time.’ Then he told me how he really likes strong and smart women like me. Disgusted and outraged, I said no firmly again, pushed him away and made sure he was out my door.”

When McClure apologized a year later in a Facebook message, it was “half-hearted”, according to Sew Hoy: “I was disappointed that he used words like ‘If that incident last year made you feel uncomfortable, I’d like to apologize,’ and ‘if I misread things or acted inappropriately.’ If? It showed me that he did not think what he did was wrong, was not remorseful, did not own up to it and it was not a sincere apology.”

Sew Hoy hopes that her story will lead investors to create clear policies around sexual harassment and discrimination.

“It will also lead to more awareness and make anyone think twice about making a move. People who did in the past must be shitting their pants right now.”

Asked for comment on Sew Hoy’s blogpost, 500 Startups said in a statement: “We appreciate Cheryl speaking up and realize how upsetting and painful it is for her to have gone through that experience and have the courage to speak up. We can only hope our efforts in changing 500 can help create a safe and effective platform for female founders around the world.”

Two of 500 Startups investors, Freada Kapor Klein and her husband Mitch Kapor, said that the tech ecosystem is a “sector gone deeply awry”.

“This is not just a case of a few bad actors. This is not something that is fixable with a pledge or a new policy,” they said in a statement.

“This is a culture that has been allowed to fester and to rot by enablers who refused to intervene when they witnessed inexcusable behavior or went to great lengths to avoid seeing it.”

• If you would like to share stories of discrimination and harassment in Silicon Valley, email sam.levin@theguardian.com or olivia.solon@theguardian.com