What happened at the Presidents Club was young women being used as bait for wealthy and powerful men. Young “hostesses”, told to wear black underwear and high heels, working at a raucous all-male dinner. The perfect environment for sexual harassment – exposed by young female journalists from the Financial Times. While the Presidents Club may seem an extreme example, we know that women face this sort of behaviour every day and night in workplaces across the UK. TUC research found that more than half of female workers have experienced sexual harassment. And Unite, the country’s biggest union, has recently found that nine out of 10 workers in hospitality have experienced harassment.

The women employed as “hostesses” by the Presidents Club were predominantly young. They were all employed through an agency. Many of them probably rely on jobs like this to pay their rent, and worry that if they complain they won’t be offered further work. Worse, the women working at the event were made to sign non-disclosure agreements (NDAs) beforehand. The organisers clearly expected bad behaviour from their all-male guests – but they were more concerned about the event’s reputation than about the wellbeing of their staff.

Scaring workers into staying silent cannot become common practice

The women weren’t given time to read the contents of the NDAs they had to sign, and didn’t even get a copy for themselves. They may well have got the impression that they had signed away their right to complain about inappropriate – not to mention illegal – behaviour. But agency workers still have rights. Your statutory protections against sexual harassment can’t be signed away. And in today’s world of work, it should go without saying that all women workers deserve to be treated with respect. NDAs cannot be used to sweep abusive behaviour under the carpet.

Now the government is going to review this use of NDAs. And unions will use every opportunity to influence the review and make sure that this misuse is stopped. Scaring workers into staying silent cannot become common practice. We need other changes too. Employers should be made responsible for protecting staff from harassment by clients and customers. While existing rules on vicarious liability provide some protection, a strong new law would send a clear message that employers need to set out to protect their staff from harassment and abuse before it happens.

Four out of five women in the TUC’s survey didn’t report the harassment to their employers. If women don’t feel safe and confident to talk about the harassment and abuse they face, then we can’t stop it from happening. That’s where trade unions come in. We can negotiate workplace policies to promote dignity at work and make sure allegations of sexual harassment are taken seriously. And every day, union reps around the country provide practical and emotional support to victims, guiding them through official processes and accompanying them to meetings with employers.

We want no one to face the threat of harassment, violence or degrading treatment. And we’re proud to stand with all of those women who’ve spoken out in the last few months. It’s time to shine a light into the dark spaces where misogyny and abuse continue to thrive – male-only events, private members’ clubs, sports clubs. The government’s review must make sure that NDAs cannot be used to protect wealthy and powerful men who mistreat female workers.

Change won’t be easy. And it’s not just up to women. Hundreds of men attended the event, but only spoke out about harassment when a newspaper exposed it. How can so many of them claim, straight-faced, that they left before anything untoward happened? I don’t believe it. We should expect more of men in our workplaces and in our communities. It’s time for us all to step up and call out sexual harassment.

• Frances O’Grady is general secretary of the TUC