The rise of the "bromance" could threaten heterosexual relationships, academics have warned, after discovering that many men find their close male friendships more emotionally satisfying than relationships with women.
Intense male friendships have grown more acceptable in recent decades as attitudes towards homosexuality changed, meaning men no longer fear showing affection towards each other.
But researchers at the University of Winchester warned that bromances, coupled with the ease at which men can now engage in casual sex, are threatening long term relationships with women.
After surveying 30 undergraduates, they discovered that 28 would rather talk about emotional issues with their male friends rather than girlfriends. The majority also said it was easier to resolve conflicts with men, and admitted they kept secrets from partners which they shared with male friends.
Dr Stefan Robinson, of the University of Winchester, said the results were "significant and worrying" for women and warned there is in emerging culture of sexism and disdain in the way Millennial men view the opposite sex.
"These heterosexual millennial men cherish their close male friends, so much so that they may even provide a challenge to the orthodoxy of traditional heterosexual relationships," said Dr Robinson.
"Given that young men are now experiencing a delayed onset of adulthood, and an extended period of adolescence, men may choose to cohabit as a functional relationship in the modern era.
"Because heterosexual sex is now achievable without the need for romantic commitment, the bromance could increasingly become recognized as a genuine lifestyle relationship, whereby two heterosexual men can live together and experience all the benefits of a traditional heterosexual relationship."
The researchers say films such as 21 Jump Street (2012), Due Date (2010) and The 40-Year-Old Virgin (2005) have also heralded the era of the "Lad flick" which has made close friendships between men normal and desirable.
All the men involved in the study had had "bromantic" friends who they lived with, and had known for at least 18 months.
Of the 30 men interviewed, 29 said that they had experienced cuddling with a same sex friend, and many said they often slept in the same bed.
One man named 'Aaron' told researchers: "We hug when we meet, and we sleep in the same bed when we have sleepovers. Everyone knows it, and nobody is bothered by it because they do it as well."
Another man surveyed, called 'Martin' said: "It's like having a girlfriend, but then not a girlfriend.
When asked to describe the difference between a "bromance" and a romance, one undergraduate called 'Bob' answered: "Sex really. That's all."
Most men surveyed said they also told their male friends secrets which they felt unable to share with their girlfriends.
One participant named 'Harvey' said: "Well, for example, Tim knows I love listening to Taylor Swift and Beyonce, but I keep that quiet because she would judge me. I feel like I have to be more manly around her."
Dr Robinson added: "Young heterosexual men are now able to confide in each other and develop and maintain deep emotional friendships based on intimacy and and the expression of once-taboo emotional sentimentality.
"There are however significant and worrying results here for women. These men perceived women to be the primary regulators of their behavior, and this caused disdain for them as a whole in some instances.
"Much in the same way that women are portrayed in contemporary cinema as objects for male gratification several of the participants spoke of women they knew in a generally negative way."
The research was published in the journal Men and Masculinities.