A claim for sex discrimination, thought to be the biggest ever involving a transsexual, is due to go to tribunal next week.
Jessica Bussert, formerly known as Josh, is seeking £500,000 from Hitachi Data Systems under the Sex Discrimination (Gender Reassignment) Regulations 1999.
She is also suing Hitachi in the US for $3.6m (£1.93m) damages over claims the company demoted her from her high-level IT job after she had facial and breast surgery.
Hitachi Data Systems denies all charges.
The regulations apply to any employee who intends to undergo gender reassignment, is going through the process or has already done so.
After taking six weeks off for the facial feminisation and breast surgery in March 2005, Bussert claims she was effectively demoted because she had to report to a different person who had previously been hired as her equal and was given basic administrative tasks normally performed by secretaries. Her salary remained the same at £88,000.
The case, which is due to start on Monday, is expected to run for 10 days. Her California case is currently being prepared for filing.