Seventy-five rape allegations and 150 alleged sexual assaults have been reported to military police in the last three years, following the suicide of Corporal Anne-Marie Ellement, 30, who was found hanged at Bulford Barracks in Wiltshire in 2011.

All the fresh allegations were made by serving members of the armed forces or Ministry of Defence (MoD) civilian staff against colleagues.

Ellement's death came two years after she was told there was no chance of securing convictions against the two men she accused. She was then allegedly subjected to bullying by female colleagues, including the girlfriend of one of the accused.

Her sister Khristina Swain said she believed there had been a cover-up: an inquest into Ellement's death has just been delayed after MoD lawyers found 1,400 previously unseen documents.

Some campaigners, such as Lisa Langstaff of "Women Against Rape", believe investigations into sexual assaults within the armed forces should be investigated by civilian police rather than military police because of a tendency to sweep matters under the carpet:

"There's no oversight; no public accountability," says Langstaff. "If you report it, it's like you're breaking ranks. It's gone beyond one or two victims who had a hard time: this is a systemic problem."

Despite the number of allegations, the conviction rate for sex crimes within the military is low. Between October 2011 and November 2013 five servicemen were convicted of rape, 22 of sexual assault. Despite these figures the MoD says sex abuse allegations are falling and that "every allegation is thoroughly investigated".

Since the unexplained deaths of four young soldiers at Deepcut Barracks in Surrey, tales of systematic bullying and sexual assault have surfaced on a regular basis within the armed forces. The first woman to join the Beefeaters, Moira Cameron, hit the headlines when she was subjected to a bullying campaign by colleagues, two of whom were disciplined.

Labour MP Madeleine Moon believes many sex crimes still go unreported.

"The military is one of the last closed institutions in this country that hasn't adapted to modern social values," says Moon. "As more and more women enter the military, we need to drive out old attitudes around bullying and sexual harassment. The trauma can be horrific. For too long it has been something you 'manned up' about. The attitude is: don't rock the boat."