The outgoing Labor boss Kaila Murnain has slammed her party’s inability to grapple with its “nasty culture of sexism” and urged it to pursue “real and lasting reform” to improve integrity.

Murnain formally announced her resignation as NSW Labor general secretary on Thursday following explosive evidence heard at an anti-corruption probe that she had kept quiet for almost three years about unlawful donations from the Chinese billionaire Huang Xiangmo.

Murnain was suspended in August from the position she had held since 2016, when, at 29, she became the first woman to hold the top job in NSW Labor.

“The circumstances leading up to my election in 2016 were horrendous,” she said.

“Some of these events were reported in the media at the time, and some of these events have received more recent attention.

“However, I believe it is inarguable that our party has never fully grappled with the nasty culture of sexism which women face in politics.”

Murnain’s predecessor, Jamie Clements, had resigned in the wake of accusations of sexual harassment, which he denied. Clements told an Icac inquiry recently that Murnain “hates my guts”.

Murnain came under significant pressure during hearings of the Independent Commission Against Corruption, which was examining whether Huang, a banned donor, gave $100,000 cash to NSW Labor in 2015.

The commission has heard the cash donation was brought into NSW Labor headquarters in an Aldi shopping bag during Clements’ time as general secretary, and was later covered up using a series of false disclosures from fake donors.

Murnain said she had learnt of the Huang donation in 2016, after an evening meeting with the former Labor MP Ernest Wong outside state parliament. Acting on the advice of then Labor senator Sam Dastyari, Murnain said she sought out the party’s lawyer, Ian Robertson, who allegedly told her to keep quiet and do nothing further.

“At the end of the conversation, Ian said to me ‘there is no need to do anything from here’,” Murnain said at the Icac inquiry. “‘Don’t record this meeting. Don’t put it in your diary. Forget the conversation happened with Ernest. I won’t be billing you for this either … and don’t tell anyone about it.’”

Robertson flatly denies giving any such advice.

Murnain was suspended following her evidence to Icac.

On Thursday, Murnain pointed to the work she had done to improve party integrity. She said she had presided over three independent reviews and acted on their recommendations, including by banning cash donations, introducing real-time donation disclosure, creating a code of conduct, appointing a governance director, and training staff and creating policies.

“There has been a lot said recently about the culture of the party. Over the past three years we have worked incredibly hard to improve that culture, however, it is clear more work needs to be done to grapple with legacy issues in the 128 year old organisation.”

The Sydney Morning Herald this week reported Murnain’s payout would be about $700,000.

Murnain said she and her family had been through “an incredibly difficult time” and slammed much of the media reporting as inaccurate.

“I dedicated my entire life to Labor. I am devastated to leave. I’m sorry to have let you down.”