The lawsuit, filed in a San Francisco court, says Google discriminates against female staff with lower pay, more limited promotion, and fewer advancement opportunities compared to men with comparable qualifications.

Ms Ellis, for example, was hired in 2010 at a level typically assigned to college graduates, although she had four years of experience, according to the lawsuit. A male colleague with similar levels of experience started on a higher rung.

She was also assigned to a less prestigious engineering role, the suit says

Ms Ellis resigned from Google four years later "because of the sexist culture", the lawsuit said.

Previous allegations

The complaint is seeking class-action status that would cover women working at the company in California for the last four years. They are looking for unpaid wages, among other remedies.

Google said it would review the lawsuit but disagreed with the "central allegations".

"Job levels and promotions are determined through rigorous hiring and promotion committees, and must pass multiple levels of review, including checks to make sure there is no gender bias in these decisions," spokeswoman Gina Scigliano said in a statement.

Like other companies in Silicon Valley, the company has faced questions about how it treats women before.