Pentagon figures have shown that woman make up a disproportionate number of those being fired under the US military gay ban.

According to research by the Palm Center, a University of California institute, women are discharged at three times the rate of their male colleagues.

Last year, 56 of the 90 total Air Force discharges were women, even though women make up only 20 per cent of the service.

In the Army, where women make up 14 per cent of servicemembers, 36 per cent of those who were fired were female.

In the Navy, women account for 14 per cent of the service but made up 23 per cent of the firings and in the Marines, 18 per cent of those fired were female, while only six per cent of the service are women.

In the total 619 discharges across the military last year, just over a third were women. They account for 15 per cent of servicemembers.

Dr Aaron Belkin, director of the Palm Center, said: “We have always known that women are disproportionately affected by ‘don’t ask, don’t tell.

“But the Air Force data are particularly troubling and raise questions about why women might be targeted there for persecution under the current policy. “

Palm Center researcher Nathaniel Frank told Associated Press that one partial explanation could be that women in the military were more likely to be gay than their male counterparts.

However, he added that a number of investigations could arise from male colleagues harassing women for being lesbians or rebuffing their advances.