The Hollywood A-listers' "buddy movie" Wolfs has received scathing reviews from critics who've branded the picture "uninspired and lifeless".
And now RadarOnline.com can reveal the actors have fallen out because of it, courtesy of an "immature blame game" over the movie's disastrous reception.
A Hollywood insider said: "George is starting to feel like every time he tries to do something with Brad, it blows up in his face.
"And Brad is getting tired of being his buddy's whipping boy."
The movie – released this week in cinemas before being made available on AppleTV+ – concerns two former boxers, played by Pitt and Clooney, who put their rivalry aside and work together.
But the film was savaged by critics, one of whom described Wolfs as a "vanity project" for the superstars, while another labeled it "shockingly bad".
The Ocean's Eleven stars have reportedly rebuilt their friendship in recent years after it "cooled" while Pitt – whose rep dismissed feud talk with Clooney as "preposterous" – was in a relationship with former wife Angelina Jolie .
It's been claimed Jolie never approved of the pair's closeness and considered Clooney's international human rights lawyer wife Amal "a wannabe who was treading on her territory as a globe-trotting do-gooder".
An insider said: "Ange always felt threatened by Amal and her impressive pedigree.
"She immediately took a dislike to her and made it impossible for George and Brad to spend time together."
The strain between the couples allegedly got so fierce Pitt snubbed the Clooneys' wedding in 2014.
An insider added: "That was a real blow for George.
"It took him a long time to rebuild trust in his old buddy."
However, the pair reportedly grew close again during Pitt and Jolie's marriage struggles as Clooney gave his pal advice and comfort as the divorce turned toxic.
The insider continued: "George couldn't stand by and let Brad be beaten up like that in the public eye.
"He made himself available to Brad for emotional support and their friendship got a second wind."
With their bromance back on track, the pair pledged to work with each other again – for the first time since their 2008 movie Burn After Reading .
But the link-up has proved to be a disaster.
The Hollywood insider added: "Now it's all blown up in their faces.
"Neither has had a significant hit in years, and now this mega-disaster has thrown a grenade into their happy reunion."
Speaking during a press conference at the Venice Film Festival , where Wolfs premiered last Sunday, Clooney admitted working with friends has become increasingly "important" to him.
He said: "We kind of figured there's gotta be a good reason to get back in a film together, something we feel like we could build upon what we've done before.
"But also, I gotta say, as I get older, working with the people that I just really enjoy spending time with has really become important to me."
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