Roberta Kaplan has resigned as chairwoman of Time’s Up after facing widespread criticism for allegedly advising New York governor Andrew Cuomo’s administration on sexual harassment allegations against him.

Kaplan, a prominent lawyer who founded Time’s Up legal defense fund and represents the writer E Jean Carroll in a defamation lawsuit against Donald Trump, resigned on Monday, becoming the latest prominent figure to quit in the wake of the scandal engulfing Cuomo.

Time’s Up was set up in response to the #MeToo movement to promote gender equality. The news was first reported by the New York Times and confirmed by the organization.

Last week a report from the New York attorney general found Cuomo had sexually harassed 11 women, and that found Kaplan had reviewed a draft of an op-ed letter aimed at attacking Lindsey Boylan, a former aide of the governor and the first to publicly accuse him of sexual harassment. The letter was never published, but was part of a broader effort by the governor’s inner circle to discredit Boylan, the report found.

On Sunday a senior aide to the governor, Melissa DeRosa, who was found to be a central part of the effort to retaliate against Boylan, resigned from the administration.

According to the Times, Kaplan announced her resignation by letter on Monday, stating that as a practicing attorney should could not openly answer questions about her involvement with Cuomo or DeRosa.

“I therefore have reluctantly come to the conclusion that an active law practice is no longer compatible with serving on the Board at Time’s Up at this time and I hereby resign,” Kaplan wrote, according to the Times.

Her resignation came as a group of 40 sexual assault survivors posted an open letter to Time’s Up, criticising both Kaplan and the organization’s CEO, Tina Tchen, who is also named in the attorney general’s report.

“We write to you as a collective group of survivors and victims who believe Time’s Up is failing the survivor community. We believed in your mission and hoped that your investment in eradicating sexual assault and harassment in the workplace would change the tide to support us as we came forward, but we are disappointed,” the letter states.

It also calls for a third party investigation “illustrating the full extent to which TIME’S UP board members and staff members have been approached by, offered advice to, or are representing perpetrators of harm.”

In a statement Time’s Up said Kaplan’s resignation was “the right and appropriate thing to do”.

The attorney general’s report found that Cuomo groped, kissed or made suggestive comments to 11 women in violation of the law, prompting local prosecutors to launch a criminal investigation and reigniting calls for him to resign or be impeached.

The investigation, which took almost five months to complete, interviewed 179 people and was conducted by two outside lawyers, found the Cuomo administration was a “hostile work environment” that was “rife with fear and intimidation”.

Cuomo’s attorneys have attempted to attack the integrity of the report as the governor seeks to cling to his position, despite mounting bipartisan calls for him to resign. The New York assembly is considering articles of impeachment against the governor.