One of the women, Mary Singleton, has been complaining about the inequality for 20 years and says that in 1986 the lab's management board admitted that female staff were discriminated against. However the board took no action. Singleton, who retired last year, used to manage Livermore's plutonium facility. "The regents and management at the lab have known about this problem for a very long time and have simply refused to take appropriate action, " she said.

Another of the women, Maura Spragge, was worried about the message being sent to would-be women scientists. "When we entered this field, we thought we were breaking something open, " she said. "But I wouldn't encourage a young woman to go into it with conditions as they are now."