Now Americans can sue if their boss is sleeping with someone else

The ruling, on a case arising from the California prison system, greatly expands the definition of sexual harassment because it can now apply to people who have no sexual interaction whatsoever. Other American courts, at both state and federal level, have considered this broad definition in the past but have never before accepted it. Ronald George, California's chief justice, wrote in the court's unanimous ruling that what was at stake was not so much sex as the creation of a workplace atmosphere demeaning to women "because a message is conveyed that managers view women as 'sexual playthings'."

The case in question was an eye-popping one. The warden of a women's correctional facility in California's Central Valley was accused by two subordinates of having simultaneous extramarital affairs with three female employees and giving them preferential job treatment. Not only did the plaintiffs, both women, say they were consistently overlooked for promotion; they also suffered retaliation when they complained.

An internal investigation a few years ago found the warden's behaviour "was broadly known and resented in the workplace". The warden, Lewis Kuykendall, retired shortly after the investigation. One of his alleged lovers, who resigned rather than face disciplinary charges, was cited in the court ruling as bragging about her affair with the boss and saying he would have to promote her if he didn't want her to "take him down" by naming "every scar on his body".

The same alleged lover was also accused of taunting the plaintiffs and, on one occasion, pinning one of them against a filing cabinet and refusing to let her leave for two hours. The plaintiff, Edna Miller, filed a formal assault complaint with the warden the next day, but Mr Kuykendall ignored it.

Both Ms Miller and her fellow plaintiff, Frances Mackey, said their working life was made uncomfortable, leading to acute stress and illness. Ms Mackey died in 2003, leaving her estate to take over her side of the suit.

When California's lower courts heard the case, they acknowledged that the warden's behaviour may have been unfair but was not necessarily discriminatory. The ruling by the state Supreme Court is likely to have a sweeping effect on employment practices throughout the state because a boss considering an affair with a subordinate will not only have to consider the impact on his prospective partner but on everyone else in the office too.

The Hollywood casting couch - where sexual favours were once routinely expected of budding starlets - has thus been rejected once and for all.