Women who were key to exposing the disgraced Hollywood film producer Harvey Weinstein have told of their frustration at the decision by UK prosecutors to discontinue two indecent assault charges against him.

Zelda Perkins, a former personal assistant to Weinstein who broke a non-disclosure agreement (NDA) to help expose him as a rapist, said the decision called into question the justice system’s attitude towards sexual assault and rape.

“It’s about how the Crown Prosecution Service balances what it’s going to cost them in terms of resources and the likelihood of a conviction,” she said.

The CPS announced this month that it was discontinuing the charges of indecent assault against a woman in London in 1996 after a review of evidence found “there is no longer a realistic prospect of conviction”.

Perkins, who said she had asked the police to return pieces of evidence including diaries and tapes relating to Weinstein, said she believed the UK developments were partly influenced by recent events in the US, where Weinstein’s 2020 conviction for sex crimes was overturned by a New York appeals court. He is due to be retried and now also faces new charges there.

“What happened in the US is not about his guilt,” she said. “There was a legal technicality and all that does is highlight, yet again, that this is about the disparity of power. If you are wealthy, you can afford lawyers, you will continue looking for smaller and smaller and smaller legal loopholes.

“I don’t think that was the sole reason but it fed into the decision here. There is a huge issue with the British justice system and the ability of the CPS to deal with rape and sexual assault and where they consider it’s worth spending money pursuing cases.”

Rowena Chiu, who was also an assistant to Weinstein and who publicly accused him of attempting to rape her in Venice in 1998, said it had been her understanding that British prosecutors were waiting to see how the trials in the US would go.

“But it does appear the case that the logistics and the cost and the barriers to getting very powerful, wealthy men convicted remains a deterrent,” she said.

“It is disheartening that the balance of power is so tipped against survivors, who have to jump through what seems to be an extraordinary set of hoops in order to get a conviction and to get a conviction to stick.

“Legal reform is needed to shift that balance. But I also take an optimistic view. [The New York case] is not over and there are other brave women willing to come forward. I’m constantly impressed by the conviction of people who will not give up and I hope that that is a signal to the world at large that this is a reckoning. This is a new moment. It’s an answer to everyone who said that #MeToo will be flash in the pan. It’s a decade later. We’re still here.”

The CPS decision would be “hugely disheartening” to victims of sexual assault, said Perkins, the co-founder of Can’t Buy My Silence, an organisation campaigning against the use of NDAs.

But she added: “The root of this issue is much broader than weak men’s proclivity for sexual assault. It has to do with the system that enables those in power to abuse and buy justice. That is far more problematic on a global scale in terms of the integrity of law. Weinstein is going to die in prison, and the headlines always follow how it’s about him not being brought to justice. But I think it’s more about systemic weakness.”

Weinstein, 72 – who is recovering from emergency heart surgery – was indicted last week on additional sex crime charges before a retrial in New York.

He was convicted in 2020 after a jury found him guilty of a criminal sex act in the first degree and rape in the third degree. He was sentenced to 23 years in prison.

A Los Angeles jury in 2022 found him guilty in a separate case on three counts of rape and sexual assault and he was sentenced in 2023 to an additional 16 years. He denies wrongdoing.