The wife of Manchester United legend Ryan Giggs reportedly tore into his ex-lover in broad daylight.
The Sun reports Giggs also laid into sister-in-law Natasha during the slanging match near Manchester.
Giggs, 37, and Stacey came face-to-face with her in the street outside a restaurant.
As Giggs, Stacey and Natasha traded insults, astonished drivers stopped their cars to watch.
A source said: "Stacey said, 'You're nothing but a f***ing slag.
"Ryan turned to Stacey and said, 'Shut the f*** up and get in the f***ing car'."
Stacey obeyed - and then furious Ryan jabbed a finger at Natasha and screamed: "Are you f***ing proud of yourself?"
The embarrassing clash came on Tuesday as Welsh midfielder Giggs and Stacey, 34, were outside the Tung Fong Chinese restaurant near their home in Worsley, Greater Manchester.
Mum-of-two Natasha, 29 - married to Giggs' younger brother Rhodri - was waiting to pick up sister Kerrie, who works nearby.
She later tweeted: "That awkward moment when u bump into the one person u never thought you would see again - with his lapdog!!"
Natasha added: "Had a blazin row in the street. He is such a t**!!!!!!!!"