Social media users started a backlash against Mia Farrow on Monday, suggesting the actress - who has accused her ex Woody Allen of being a child predator - is a hypocrite for her alleged participation in his threesomes with younger women.

Twitter users pointed out Farrow's alleged role in the movie director's relationship with Babi Christina Engelhardt, insisting she should be criticized more for being an enabler after the former model claimed she took part in drug-fueled sex with them both when she was 20.

If the story is true and Mia stayed with Allen throughout, it could beg the question of why Farrow has failed to mention it but has shared other stories about her ex that don't pose a risk to her reputation.

After the alleged Engelhardt affair, Mia would later go on to accuse Allen of sexually abusing adopted daughter Dylan Farrow and leading a narrative that branded him a pedophile.

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Woody Allen and Mia Farrow allegedly had threesomes with Babi Christina Engelhardt (Farrow and Allen in 1983, around the time the threesomes stopped between the pair)

Shocking claims: Babi Christina Engelhardt (above aged 17) was with Woody Allen for eight years, and began seeing the director when she was a 16-year-old high school student

As it emerged she may have encouraged Allen by allegedly taking part, people tweeted urging for a comment from Farrow and her son Ronan Farrow, who has exposed sexual misconduct allegations and helped lead the #MeToo movement.

The woman told The Hollywood Reporter that she was a 16-year-old high school student when she began dating a 41-year-old Allen, saying that after a few years the twice-divorced filmmaker introduced her to his new girlfriend, Mia.

Soon after, according to Engelhardt, she began having threesomes with Allen and Farrow, who is 10 years younger than Allen.

The story prompted readers to label the former partners a 'vile pair'.

'But Mia Farrow in a 3 way? Hmmm. That would make her as bad as Woody,' one Twitter user posted. Another pointed out that Ronan has helped give other women a voice but hadn't yet shown support for Engelhardt.

One tweet read: 'What is Mia and her famous son Ronan Farrow going to say? Why hasn’t he exposed this sex scandal? Ronan you believe her don’t you?'

But Engelhardt says she enjoyed Farrow's company and the two would smoke joints and discuss astrology and animals, seeing Allen's new girlfriend as a victim.

Twitter users demanded a response from Mia Farrow (right) and Ronan Farrow (left) after a former model claimed she had threesomes with Mia and Woody Allen when she was 20

A Twitter user posted that Ronan Farrow was staying quiet on the subject despite his involvement in the #MeToo movement

Twitter users pointed out that Mia Farrow could be just as bad as Woody Allen

One tweeter suggest Mia Farrow was not all there if she was involved in threesomes with the young woman

'I felt sorry for Mia,' Engelhardt says, making reference to the fact that Allen would eventually go on to betray her by having an affair and then marrying her adopted daughter Soon-Yi Previn.

'I thought, "Didn't Woody have enough 'extra,' with or without her, that the last thing he had to do was to go for something that was totally hers?"'

She then adds: 'He had groomed Mia, trained her, to put up with all of this. Now he had no barriers. It was total disrespect.'

Engelhardt claims she had group sex with other young women that Allen brought in before being introduced to Farrow.

She also explains that she was resistant about being intimate with women, but grew fond of Farrow.

'There were times the three of us were together, and it was actually great fun. We enjoyed each other when we were in the moment. She was beautiful and sweet, he was charming and alluring, and I was sexy and becoming more and more sophisticated in this game,' recalls Engelhardt of the time.

'It wasn't until after it was done when I really had time to think of how twisted it was when we were together … and how I was little more than a plaything.'

She adds: 'While we were together, the whole thing was a game that was being operated solely by Woody so we never quite knew where we stood.'

Teen queen: Engelhardt says she was hesitant at first to be intimate with a woman but grew to like Farrow as they smoked weed and talked about astrology during the trysts (the former model in 1977 at the age of 17)

'I used to think this was a form of mother-father with the two of them,' says Engelhardt

Allen and Farrow both declined to comment.

At first, Engelhardt says she was upset to be meeting Allen's girlfriend since she was under the impression that she was in a relationship with the director.

'I felt sick. I didn't want to be there at all, and yet I couldn't find the courage to get up and leave. To leave would mean an end to all of this,' she writes in a manuscript for her memoir, which she shared for the first time.

'Looking back now, that's exactly what I needed, but back then, the idea of not having Woody in my life at all terrified me.

'So I sat there, patiently, calmly trying to assess the situation, trying to understand why he wanted the two of us to meet.'

The relationship also took on another surprising element according to Engelhardt.

'I used to think this was a form of mother-father with the two of them,' she says of her time with Allen and Farrow.

'To me, that whole relationship was very Freudian: how I admired them, how he'd already broken me in, how I let that be all right.'

Farrow (right in April 2016) has accused Allen of sexually abusing daughter Dylan Farrow

Woody Allen has been criticized because he went on to marry his adopted daughter Soon-Yi Previn (pictured July 2016)

Her relationship with Allen was confirmed by her brother and the photographer she was with on the night she gave the filmmaker her number.

She also shared a letter she received from the director recalling their relationship fondly and asking her to meet his new wife in 2001 after she sent him a documentary on Federico Fellini.

Farrow ended her relationship with Allen in 1992 when she found nude photos he had taken of her adopted daughter Soon-Yi Previn.

In an interview earlier this year, Previn said that what Farrow then did began the narrative that has lasted for almost three decades.

Previn was then kicked out of the house but then let back in, though she believes that she was being followed by an private eye hired by Farrow.

Previn's relationship with Allen continued in secret, while Farrow sent Allen a 'gothic' Valentine a month later that showed he heart with a knife through it and their children on skewers.

Farrow and Allen were also still working together on what would be their final film together, Husbands and Wives.

Previn and Allen stayed in touch when she went to work at a camp that summer, and by August she had been kicked out for talking on the phone too much with a 'Mr. Simon.'

Farrow seems to have discovered the two did not separate on August 1, when she reportedly called psychologist Susan Coates and said that she needed to 'find a way to stop' her 'satanic and evil' ex.

Three days later, Farrow's adopted daughter Dylan Farrow was allegedly abused by her father in an attic crawl space.

It was a week later that Allen claimed Farrow's lawyers offered him a confidential settlement agreement that would have buried the allegations for $5 to $7 million.

In contact: She also shared a letter (above) she received from the director recalling their relationship fondly and asking her to meet his new wife in 2001

Celluloid tribute: She claims their relationship was the basis for the 1979 film Manhattan, starring Meryl Streep, Diane Keaton, Allen and Mariel Hemingway (above with Allen in the film) as his girlfriend

He responded by suing Farrow in court for custody of Ronan as well as Moses and Dylan.

Allen had an uphill battle as in addition to the abuse claims he had only became the father of Dylan and Moses in December 1991, just a few months prior and right around the first time he admitted to having sexual relations with Previn.

Farrow had agreed to the adoption at Allen's insistence with the director asking her to allow him that role because she wanted to take in another child.

A team of three investigators from Yale–New Haven Hospital came to the conclusion that Dylan had been coached by Mia in 1993, but the judge still ruled against giving Allen custody.

The director also lost his appeal, despite New York State child-welfare investigators finding no evidence of any misconduct on Allen's behalf in a second probe into the allegations.

Allen and Previn married in 1997 and later adopted two daughters who are now teenagers.