Madonna and Diana Ross' feud REVEALED: What REALLY caused the falling-out between the Queens of Pop and Motown?

• READ MORE: Madonna's MANY feuds exposed 

Over decades of superstardom, Madonna has richly earned a blistering reputation for her claws-out feuds with her pop peers. 

She infamously locked swords with the likes of Cher, Elton John, Lady Gaga, Gwen Stefani, Janet Jackson and Mariah Carey, among many, many others.

But even diehard Madonna fans may have missed the Queen Of Pop's catfight with the Queen Of Motown - Diana Ross herself.

On the surface the two songstresses seem birds of a feather, with their shared roots in Michigan and their common experience of stratospheric fame.

However DailyMail.com will now lift the curtain back on their fraught equation, traced back to the incident Diana vowed she 'won't forget'... 

Both women grew up in the Detroit area, Madonna in the suburbs of Pontiac and Rochester Hills and Diana in town, including for some years in the projects.

As a child in the 1960s and 1970s, Madonna was enraptured by the Motown music scene that emerged from Detroit and swept the globe. 

The reigning female star in the Motown orbit was Diana, as the queen bee of the thunderously popular girl group The Supremes. 

During an interview early in her career, Madonna cited Motown as an influence on her own work, adding: 'Diana Ross was a real big inspiration for me.'

By the 1990s, Madonna was a megastar - but it was Diana who was named the 'most successful female performer of all time' in the Guinness Book Of World Records.

When Diana appeared on TFI Friday in 1999, host Chris Evans brought up her Guinness accolade and joked: 'I bet Madonna hates you, doesn't she?'

'No, I -' said Diana, breaking into a laugh and confessing: 'She might!' then adding that she was personally acquainted with Madge.

Chris vamped that Madonna was a 'flash in the pan' next to Diana, who diplomatically demurred: 'No, she's been around. She's got some legs, yeah?'

Four years later, Diana offered a more unfiltered - and rather more negative - view of Madonna from Graham Norton's couch. 

Graham asked whether she was a 'fan' of Madonna and, observing Diana's visible discomfiture and long pause, giggled: 'I'm sensing not.'

'Well, my kids went up and asked her for an autograph, and she was not nice,' said Diana. 'And I won't forget it. So that's it. That's what I feel about that.'

Diana, who over the years has been accused of some formidable diva behavior herself, said that Madonna 'wasn't nice' to Diana's children 'and I'm nice to everybody, you know, and I just feel like she could've been nice, but she wasn't.' 

About a decade later, however, Madonna appeared to take a warmly nostalgic view of her past encounters with Diana.

In 2015 she posted a throwback snap of herself in the early 1980s with Diana, Nile Rogers and Madonna's then-boyfriend John 'Jellybean' Benitez.

'Nile Rodgers, Diana Ross, Jellybean and me wearing a skirt Keith Haring. Painted for me! Doesn't get much better!!' Madonna wrote with a heart emoji.