The British model and actress tweeted on Thursday: “Because I felt ashamed of what happened and didn’t want to publicly ruin someone’s life, even though they privately ruined mine #WhyIDidntReport.”
The hashtag has gathered momentum in the wake of the sexual misconduct allegations against Brett Kavanaugh, President Trump’s candidate for the US Supreme Court. He denies all the allegations against him.
Women began sharing their #WhyIDidntReport stories after Trump dismissed the claims and questioned why Christine Blasey Ford, who says a drunk, teenage Kavanaugh sexually assaulted her at a high school party in the 1980s, did not immediately report the attack.
Mr Kavanaugh denies the allegations, calling them “completely false”.
Mr Kavanaugh, who has been accused of improper behaviour by at least three women, is due to testify before the US Senate’s judiciary committee on Thursday.
Delevingne, 26, did not name her attacker in her tweet on Thursday, however last October she accused disgraced movie mogul Harvey Weinstein of inappropriate sexual behaviour.
In a post on Instagram, she claimed Weinstein invited her to meet him at a hotel to discuss a potential film role, before asking her to kiss another woman in front of him.
She wrote: “I was so hesitant about speaking out….I didn’t want to hurt his family. I felt guilty as if I did something wrong.
“I was also terrified that this sort of thing had happened to so many women I know but no one had said anything because of fear.”
Other famous women, including Padma Lakshmi, Mira Sorvino and Ashley Judd have all voiced their experiences of alleged sexual attacks using the hashtag.
The 48-year-old actress, author and TV host wrote in the New York Times that her former boyfriend, who was seven years old than her, sexually assaulted her while she was sleeping.
The Indian-born star, who had never had sex before the alleged incident, said she did not know how to tell her family and friends she had been raped.
“I didn’t report it. Not to my mother, not to my friends and certainly not to the police,” she wrote. “At first I was in shock.”
“Soon I began to feel that it was my fault. We had no language in the 1980s for date rape.
“I imagined that adults would say: ‘What the hell were you doing in his apartment? Why were you dating someone so much older?’
“I don’t think I classified it as rape – or even sex – in my head.”