For 20 years, Harvey Weinstein’s former assistant kept her silence over the man who had allegedly sexually harassed her and attempted to rape a colleague.

Last October, Zelda Perkins made the fraught decision to break a non-disclosure agreement she had signed with the now disgraced movie mogul in order to expose how he had used legal contracts to suppress alleged harassment victims. Now, 10 months later, Perkins is driving a campaign calling for a ban on the use of non-disclosure agreements (NDAs) to cover up workplace crimes, including sexual misconduct and racism.

Perkins, who worked for Weinstein’s Miramax Films in the 1990s, said that amending the law to prevent NDAs being used to suppress police investigations into offences would help to stop those crimes being committed. She believes Britain should follow in the footsteps of parts of the US when it comes to the use of NDAs.

“In the US some states are trying to implement a total ban on NDAs being used in cases of sexual harassment or wrongdoing. I am leaning towards the fact that you should not be able to enter into an NDA about a crime or an instance of sexual harassment,” she told the Observer.

“The fact that these agreements can exist as a get-out way of dealing with bad behaviour in the workplace only enables that behaviour. If as an employer you don’t have that choice, you’re going to think more than twice about putting your hand up someone’s shirt.”

The fact that these agreements exist only enables bad behaviour in the workplace Zelda Perkins

Perkins has alleged that she was sexually harassed by Weinstein but having received advice from her lawyers, after confronting the disgraced movie mogul over his misconduct, felt she had no option, aged 23, but to sign an NDA.

After resigning from her job at Miramax in London in 1998, Perkins feared that she would “probably go to jail” if she broke the agreement and felt “utterly broken” that she had been silenced. She found it subsequently “impossible” to find work in the film industry.

Perkins – who recently gave evidence to parliament over the misuse of NDAs – added: “The problem with the NDA is that it has been weaponised by powerful people and by lawyers. We need to have a framework where people can work safely and where there is recourse when these individuals abuse their power.

“The law obviously has loopholes. All I am trying to do is close these and push through legislation that makes the environment more ethical – essentially it’s about power, about how we are hierarchically managed.”

In her testimony in March to a parliamentary inquiry into workplace sexual harassment, Perkins outlined aspects of her wide-ranging agreement with Weinstein, including the stipulation that she use her “best endeavours” to limit what she said to any criminal case against the film director, who has been accused by dozens of women of numerous incidents of sexual misconduct, ranging from harassment to rape.

The committee concluded that Weinstein’s agreement with Perkins demonstrated how NDAs in “settlement agreements can be used unethically and potentially unlawfully”.

The Solicitors Regulation Authority (SRA) preempted Perkins’s evidence to MPs by issuing a warning to the legal industry to halt the “inappropriate use of NDAs” and underlined the requirement to report concerns.

New figures indicate that law firms have since responded to the SRA’s call with a significant rise in the number of reports by staff of sexual misconduct by colleagues. The number of cases reported to the SRA was nine during the 12 months to October 2016, rising to 12 the year after, with 19 cases already reported this year.

Paul Philip, chief executive of the SRA, said: “It’s key that the firms, we as the regulator, and other agencies, create an environment where people can report their concerns and have confidence that they will be addressed appropriately.”

Perkins revealed to the Observer how she was “stonewalled” by a number of leading law firms after seeking legal representation once she had broken the NDA last October, shortly after a series of allegations against Weinstein surfaced in the New York Times.

“I was trying to find a lawyer because I still didn’t know if I would end up in a terrible legal situation. I went to a number of top law firms, they all spoke to me but after the initial conversation they shut me down. I was incensed and horrified by this. I was stonewalled essentially after I broke that agreement, but this is not about any particular law firm, it’s about the system,” she said.

Perkins also floated the possibility of a publicly accessible database that held the details of any company or individual who has brokered an NDA.

“Any company or individual who has made a financial settlement should be of public record,” she said. In addition, she said that it should be illegal for taxpayers’ or shareholders’ money to be used in NDA payments.

Harvey Weinstein has faced numerous allegations of sexual misconduct. Photograph: Seth Wenig/AP

The clauses attached to the Weinstein agreement signed by Perkins offer an insight into how egregious some NDAs can be. She was prohibited from even obtaining a copy of the agreement – she could only look at it supervised at a law firm’s office, a clause that also prevented MPs from acquiring the document. Ultimately she obtained the agreement in June through a personal data request. Its contents confirmed that she was banned from talking to a doctor, therapist or psychoanalyst about Weinstein’s alleged harassment unless they also signed an NDA and that she should not speak about the payment even if HMRC questioned her about it.

“If a therapist, for instance, broke the agreement, I would be held responsible for their disclosure. There were guns pointed from every angle,” said Perkins, who has since managed to rebuild her career as a successful associate producer.

Yet she also accepts that challenging the perceived potency of such agreements may take time for those who have signed them, saying that many people were afraid even to give evidence in parliament. “Even for the committee inquiry, people were too afraid to speak, some gave anonymous evidence. Many are still held in thrall to this argument. People are still afraid. This is totally wrong.”

The parliamentary inquiry, chaired by Maria Miller MP, published its findings last month, concluding that employees were being failed, by the government, employers and regulators, as current laws insufficiently protected workers.

Last week, Weinstein faced fresh allegations of misconduct when the German actor Emma Loman filed a lawsuit against him, alleging he raped her in 2006 at the Cannes film festival. Weinstein has denied all allegations of non-consensual sex.