The actor Emma Watson has urged women to understand their rights as she launched a legal advice line for those experiencing sexual harassment at work.

The Harry Potter star and Time’s Up UK activist said it was “completely staggering” that the free helpline for women in England and Wales was the only service of its type.

Pointing out that TUC research found that one in two women had experienced sexual harassment in the workplace, Watson said: “It finally feels like people are realising the scale of the problem, and I’m certainly hopeful that with global standards such as the recent International Labour Organization treaty on harassment at work we’ll start to see a new climate of prevention and accountability on this issue domestically.”

Donations from members of the public, including Watson, helped to kickstart the advice line, which is backed by Time’s Up UK’s justice and equality fund, and managed by Rosa, the UK Fund for Women and Girls. Advice is provided by the charity Rights of Women.

Watson said: “Understanding what your rights are, how you can assert them and the choices you have if you’ve experienced harassment is such a vital part of creating safe workplaces for everyone, and this advice line is such a huge development in ensuring that all women are supported, wherever we work.”

The aim of the helpline is to help plug a gap in the availability of legal advice so that women can get the right help they need to hold their employer and harasser to account.

Rights of Women’s senior legal officer, Deeba Syed, said workplace sexual harassment was a hidden problem even though it had reached “epidemic levels”.

She said: “This advice line’s purpose is to empower women to exercise their legal rights in the workplace. By advising women about their legal options and increasing their understanding of equalities and discrimination law, we will be able to help them make informed choices about next steps, including how to navigate the legal system with confidence.

“We know that complaints of sexual harassment at work are still frequently responded to in a gendered manner that is negative, undermining or can lead to victimisation. That is why Rights of Women will also work towards dismantling the underlying structural problems that puts the burden on victims and makes it difficult for women to come forward through its policy work.”

The advice line number is 020 7490 0152.