The Albanese government is being warned that one key change in a crucial bill aimed at modernising sexual harassment and discrimination laws risks undermining its positive impact.

More than 100 signatories to an open letter, including lawyers, academics and trade unions, have said proposed changes to the rules on paying legal fees in workplace harassment cases could discourage women from taking legal action and “undermine access to justice”.

Those warning against the changes include the Australian Discrimination Law Experts Group, the ACTU, Rosie Batty, the Public Interest Advocacy Centre and former top public servant Philip Flood.

Their letter was sent to Attorney-General Mark Dreyfus and Minister for Women Katy Gallagher on Friday.

The Respect at Work Bill would update 1984 laws on sexual harassment and discrimination in the workplace by implementing seven of the 55 recommendations of a national inquiry into sexual harassment in the workplace, led by Sex Discrimination Commissioner Kate Jenkins.

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The bill’s changes include placing an onus on employers to take reasonable steps to eliminate sexual harassment and discrimination wherever possible, and giving new powers to the Human Rights Commission to enforce compliance.

But the signatories warn that a new model for determining who bears the cost of legal action taken in response to sexual harassment will deter women from pursuing cases and lessen the compensation they would receive from doing so.

The bill would make discrimination cases run on a cost-neutral basis that would have individuals and their employers responsible for paying their own legal fees when making or responding to an application unless the court orders otherwise.

The letter argues that the new approach on costs will make it uneconomical for law firms to run cases on a no-win, no-fee basis and make class actions against employers unviable.

“The proposed model will ultimately make it harder for targets of sexual harassment to vindicate their legal rights,” the letter states.

“Taking a cost-neutrality approach to a relationship that is characterised by endemic inequality only serves to entrench that inequality.”

Complainants, the letter says, should only face adverse costs if they have been acting unreasonably but be able to claim back the costs of taking legal action if it is successful, like current provisions for whistleblowers.

“This model would recognise the significant inequality in resources between complainants in sexual harassment matters and their employers,” the letter states.

“The bill is a great step forward in addressing the scourge of sexual harassment in our workplaces.

“We implore you not to allow a faulty costs provision to undermine its positive impact.”

Under existing laws women who successfully sue their employer receive most legal costs back but can have costs awarded against them if their action fails.

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Commissioner Jenkins told the ABC this week that the bill’s provision giving judges discretion was an important step forward: “If it’s in the interest of justice, and so the judge can look at the financial circumstances of the parties that conduct of the parties whether anyone’s lost or won so there is an ability for, for example a complainant, to have their costs awarded.”

In 2018, one in three Australian workers had experienced workplace sexual harassment in the past five years but only 17 per cent of those who reported being harassed at work made a complaint.