In a statement released via her publicist, the 25-year-old alleged she had initially received an "uncomfortable call" from the producer, during which he questioned her about her sexuality.
"He said to me that If I was gay or decided to be with a woman especially in public that I'd never get the role of a straight woman or make it as an actress in Hollywood," Delevingne said.
"A year or two later," she added, she was invited to a meeting in the lobby of a hotel with Weinstein and another director.
The Paper Towns and Suicide Squad star claimed that, as soon as they were alone, Weinstein began to "brag" about how he "made the careers" of actresses he claimed to have slept with, before inviting her to his room.
Delevingne said she initially declined, but ended up going after his assistant insisted her car had not yet arrived.
Delevingne alleged another woman was in his hotel room, and Weinstein asked them to kiss -- before she tried to defuse the situation by asking if he knew she could sing and auditioning for him.
"After singing I said again that I had to leave. He walked me to the door and stood in front of it and tried to kiss me on the lips. I stopped him and managed to get out of the room," she added.
Delevingne said she still got a part in the film -- but "felt awful" as she "always thought that he gave it to me because of what happened."
"I was so hesitant about speaking out... I didn't want to hurt his family. I felt guilty as if I did something wrong," she added.
Writing on her Instagram page, Delevingne explained she feels "relieved" to have shared her story, and urged other women and girls to speak out if they have experienced abuse.
"In every industry and especially in Hollywood, men abuse their power using fear and get away with it," she said, adding anyone who defends abusers is "part of the problem."
From his alma mater to British politicians and the film industry, organisations are lining up to revoke the many honours bestowed on filmmaker Harvey Weinstein.
The University at Buffalo is moving to have alumnus Harvey Weinstein's honorary degree revoked in response to multiple accusations of harassment and sexual assault against the Hollywood mogul.
The university said on Wednesday it is "well aware" of the allegations against Weinstein, who was an English major there from 1969-1973.
The university says it has begun the process for revoking the honorary degree it bestowed on him in 2000. The decision lies with the State University of New York board of trustees.
In awarding the honorary SUNY doctorate of humane letters, the university noted that Weinstein and another student started a concert promotion company in 1972 called Harvey and Corky Productions, which became a fixture on Buffalo's music scene.
Multiple women have accused Weinstein of wrongdoing. He denies non-consensual activity.
Meanwhile a group of British politicians has called on the government to strip Weinstein of a royal honour bestowed on him for his contributions to the arts.
In an open letter to Prime Minister Theresa May, MPs from the opposition Labour Party said Weinstein should be stripped of his title as Commander of the Most Excellent Order of the British Empire.
The CBE is a prestigious award given out by Queen Elizabeth upon the recommendation of the government of the day. Weinstein received his in 2004.
The MPs said Weinstein's alleged sexual misconduct and abuse, detailed in stories in the New York Times and the New Yorker, were "unacceptable and intolerable. They were unacceptable in the 1960s, they are unacceptable now and they may well be criminal under US and UK law."
In light of the mounting accusations against him, Weinstein's CBE should be rescinded, the letter said. Letting him hold on to it would risk "bringing the honors system into disrepute".
On Wednesday, BAFTA announced that it had suspended Weinstein's membership for "alleged behaviour completely unacceptable and incompatible with BAFTA's values".
Weinstein denies all charges, according to a statement from his spokeswoman Sallie Hofmeister circulated among US media.
On Wednesday, Hofmeister offered "no comment" when asked about TMZ reports that Weinstein was heading to Europe to enter a rehabilitation facility.
His wife, British fashion designer Georgina Chapman, told celebrity magazine People she was leaving Weinstein, with whom she has two children.
The list of the Oscar-winner's harassment victims also reportedly now includes Gwyneth Paltrow, Angelina Jolie, Rosanna Arquette and French actress Judith Godreche.
Former president Obama and Clinton, who last year aimed to succeed him in office, finally spoke up on Tuesday, expressing revulsion at the charges against a friend and supporter.
Clinton said she was "shocked and appalled" by the revelations, while Obama and his wife Michelle said they were "disgusted."
"Any man who demeans and degrades women in such fashion needs to be condemned and held accountable, regardless of wealth or status," the Obamas said in a statement.
The comments came after days of withering accusations by Republicans that the liberal elite was turning a blind eye away from one of their own, and with President Donald Trump's party demanding that Democrats jettison contributions by the movie mogul.
"Put your money where your mouth is. Return all of the dirty Harvey Weinstein money," the Republican National Committee said Wednesday in a video that showed Clinton denouncing misogyny and former first lady Michelle Obama calling Weinstein a "wonderful human being."
Since 1990, Weinstein and his wife have personally donated more than $1.4 million to various Democratic candidates or political action committees, according to the Center for Responsive Politics.
Weinstein hosted or attended several fundraisers for Clinton last year, and has attended multiple state dinners at the Obama White House.
In 2011, he hosted an Obama fundraiser at his New York residence, where the guest list included Paltrow and rocker husband Chris Martin, television host Jimmy Fallon and singer Alicia Keys.
As Democrats began returning Weinstein money, Republicans painted liberals as hypocrites, despite many of their own party having stood by Trump when similar lurid allegations were made against him as a presidential candidate.
Trump's son Donald Trump Jr tweeted Wednesday that "maybe Hollywood will finally end their BS lectures."
The rape allegations against Weinstein, 65, were made in a bombshell expose published by the New Yorker Tuesday.
Previous allegations which led to his weekend sacking from The Weinstein Company had so far been limited to complaints about harassment.
The New Yorker investigation was published as fresh misconduct allegations emerged from Hollywood A-listers such as Jolie, Arquette and Paltrow.
Italian actress Asia Argento said Weinstein forced oral sex and intercourse on her 20 years ago.
She told the publication she had maintained her silence until now for fear that Weinstein would "crush" her, adding: "I know he has crushed a lot of people before."
Another instance involved model Ambra Battilana Gutierrez, whom the New Yorker said Weinstein met in March 2015.
According to the New Yorker, Gutierrez says Weinstein "lunged at her, groping her breasts and attempting to put a hand up her skirt" at a meeting in his offices in Tribeca.
She reported the incident and the New York Police Department asked her to wear a wire.
Audio of their conversation in a hallway at the Tribeca Grand Hotel was released by the magazine, with Weinstein heard repeatedly pressuring her to come into his room.
Authorities decided not to press charges after it emerged the young woman had attended one of former Italian prime minister Silvio Berlusconi's infamous "bunga bunga" sex parties.
As Republicans continued their criticism, many Trump critics pushed back, noting that the president himself has been accused of abusive behavior and that a tape has been released of him boasting of sexual assaults.
"It is somewhat ironic," Democratic former Michigan governor Jennifer Granholm told CNN, "that the Republicans are ginning up all of this stuff about Harvey Weinstein when the president himself has been accused of sexual harassment or sexual abuse 15 times."