The offenders are allegedly senior MEPs ranging from across the political spectrum, including former ministers.
The victims have reportedly spoken out to the Sunday Times after being emboldened to do so following the Harvey Weinstein scandal.
One young female European Parliament employee has alleged she was touched inappropriately by a nearly 60-year-old man who remains a prominent MEP.
She said: “He was stroking my hair, then my neck, going down my back… I just froze, I was petrified.
“I told my colleague, who said I should report him, but in the end I didn’t… I was afraid of losing my job, of facing the embarrassment and ruining my career.”
The offenders, who have not been named at the request of their victims, are said to fear for their careers and possible legal confrontation with their harassers.
The Sunday Times has allegedly seen a text message sent by Yves Cochet, a former French environment minister and Green party MEP, to the 25-year-old female assistant of another member.
The 71-year-old former French minister is said to have chided her for rejecting a dinner invitation and added that he wanted to share her “passions, dreams and fantasies”.
He is reported to have written: “I know it’s a cliché, an old man asking out a pretty young woman.
“But are you afraid of what people will say… do you maybe tremble with a delicious yet disconcerting expectation?”
In addition, it has been reported that one senior MEP masturbated in front of a young assistant and that another middle-aged politician groped an aide.
One 24-year-old assistant also claimed a German MEP “stalked” her in meetings and eventually made “unpleasant advances”.
Another MEP from Germany is also alleged to have indecently touched the 22-year-old assistant of a colleague at a working lunch about a political campaign.
The victim of this alleged incident has claimed that the EU parliament is “an absolute hotbed of harassment” because MEPs deliberately hire young female aides and feel they are “not accountable to anyone”.
Catherine Bearder, the Liberal Democrat MEP for South East England and a member of the parliament’s anti-harassment committee, said: “It is quite a tough job to sit there and listen to allegations of what has gone on behind closed office doors.
“When someone has power over you, you have to be pretty self-confident and have financial and other means to leave that situation… MEPs do have quite a bit of power politically and they sometimes act inappropriately.”