A 42-year-old officer is to take the Army to an employment tribunal.
Jan Hamilton claims she is the victim of sexual discrimination.
She had been appointed as head of media operations for the Army in Gibraltar but a dispute over a formal medical exam has led to the job offer being withdrawn.
Ms Hamilton says that she has had no face-to-face contact with the Army since revealing earlier this month in the Mail On Sunday her intention to undergo gender reassignment surgery.
She was told that subject to starting her job in Gibraltar, she would have to attend a medical, in male uniform.
“I have been living as a woman since January, but as far as the Army is concerned I am still a man,” she told the Mail.
“I have a male ID. It would have been humiliating and demeaning for me to turn up for my medical examination dressed in a man’s uniform.
“It’s not that I refused to go to the medical, it’s that I wouldn’t go as a man.”
Ms Hamilton says that the Army have used her change of gender as an excuse to sack her and accused them of deviousness.
“I’ll never trust them again. They’ve broken my heart. I’ve taken all my medals down off the wall.
“I risked my life for my regiment and all I wanted in return was a little respect,” she said.
Ms Hamilton served in Iraq and Afghanistan as a captain in the Parachute Regiment and is now a member of the Territorial Army.
The Ministry of Defence said: “Before a TA soldier is accepted into full-time Reserve Service, a number of processes must be completed.
“These take place at the Reservists Training and Mobilisation Centre (RTMC) and include the completion of essential paperwork, issuing additional equipment and dental checkups.
“Failure to attend the RTMC may prevent an individual from being accepted into service. An individual’s gender status is irrelevant to this process.
“There are several transgender personnel in the Army including a number who have, or are, undergoing gender reassignment surgery.”