The Equality and Human Rights Commission (EHRC) has written to all five magic circle firms to warn that it could take legal action if they fail to take appropriate action to prevent and respond to sexual harassment in the workplace.

The EHRC is sending out letters today (4 December) to Allen & Overy (A&O), Clifford Chance, Freshfields Bruckhaus Deringer, Linklaters and Slaughter and May – along with a range of other leading employers, including FTSE 100 companies – to request evidence of how they are tackling the problem of sexual harassment.

The letter warns: "Where we discover evidence of systemic failings or refusal to engage with us, we will consider exercising our statutory enforcement powers."

Those receiving the letter are being asked to supply evidence of "existing and planned systems, processes, safeguards and workplace culture in relation to sexual harassment".

The EHRC is also calling on firms to "delegate responsibility for ensuring a shared understanding and effective implementation of the legal guidance on sexual harassment, as defined in the Equality Act 2010".

Those receiving the letter have until 19 January to respond.

The letter states: "Recent high-profile testimonies demonstrate pervasive sexual harassment in contexts as diverse as Hollywood and Westminster, and the lack of redress for those women and men who experience it. The EHRC is gathering evidence on the most effective means to prevent and respond to this issue.

"As an employer, your organisation is legally liable for sexual harassment suffered by your employees in the workplace and you have a duty of care to take all reasonable steps to prevent it.

"We look forward to engaging with responsible employers to drive positive change in Britain's workplaces. We are engaging with a range of organisations, including FTSE 100 and large private businesses, government and other public sector bodies, cultural institutions, charities and universities."

The Harvey Weinstein scandal has thrown the issue of sexual harassment into the limelight, with more than 50 women accusing the Hollywood producer of a range of offences. In the wake of these revelations, allegations are continuing to surface, implicating a range of high-profile individuals from the worlds of media, entertainment and politics.

A recent Legal Week survey found that nearly two thirds of female lawyers have experienced some form of sexual harassment at work, with the majority of the incidents of harassment coming at the hands of partners.

In October, A&O's name was drawn into the Weinstein scandal by a Financial Times report which revealed that the firm had advised Miramax in relation to claims made against Weinstein in 1998. The magic circle firm was drafted in to advise the entertainment company – which was co-founded by Weinstein – when his former assistant accused him of sexual harassment.

EHRC chief executive Rebecca Hilsenrath said: "Sexual harassment is rife across all of our industries. Accountability lies with leadership. It is not enough to report a nil return.

"We need to take responsibility to ensure that no woman will ever be intimidated from reporting, be challenged by the difficulty of doing so or frightened of the implications for her career. We want to find out what is working and what the barriers are, and identify the leaders who are making a difference."