A former associate at Fried Frank Harris Shriver & Jacobson is set to file a $50m (£31m) lawsuit accusing the US firm of denying her a promotion to partner because she is a lesbian and doing nothing to stop management from harassing her, reports The Am Law Daily.

Julie Kamps, who plans to file the lawsuit this week, claims that a female partner at Fried Frank sexually harassed her. She also alleges that the firm instructs lawyers to write exaggerated negative performance reviews about associates the firm wants out.

Kamps, a graduate of Harvard Law School, worked at Fried Frank from 1998 until she was laid off in January 2009.

In the complaint, Kamps claims that Janice Mac Avoy, a litigation partner, "knowingly made unwelcome sexual advances and sexual comments to Kamps, both alone and in the presence of others." Mac Avoy allegedly "told Kamps it was 'the biggest regret of her life' that she had not slept with Kamps 'when she had the chance,'" and discussed various sexual acts with Kamps, the complaint states.

Kamps also alleges that Mac Avoy encouraged her to "wear women's clothes," because William McGuinness, chair of the firm's litigation department, believed Kamps's preference for men's shirts could "make clients uncomfortable."

The complaint names both Mac Avoy and McGuinness as defendants. It also names David Hennes, a litigation partner who, Kamps alleges, asked her to write a negative review of a lawyer that the firm was "trying to get rid of," the complaint says. Kamps refused to write the review, and she claims Hennes began harassing her as a result of her refusal.

Fried Frank laid off Kamps in the middle of an arbitration session in January. It is unclear why Kamps was fired at that time, and Kamps claims in her lawsuit that she has never received a negative performance evaluation or a solid reason for her dismissal.

In addition to the $50m, Kamps is seeking to be reinstated to Fried Frank as a partner.

The complaint also names Justin Spendlove, the firm's managing partner, and 100 other defendants. Kamps declined to comment, other than to say she has not yet decided whether she will represent herself in the case.

The Am Law Daily is the website of The American Lawyer, Legal Week's US sister title.