Solange ATTACKED Jay-Z after he said he was going to Rihanna's party WITHOUT Beyoncé

Beyoncé's sister Solange lashed out at Jay-Z in an astonishing elevator attack after the music mogul said he was attending Rihanna's Met Ball after-party without his wife, it has been reported. (click here to watch video)
According to the New York Daily News, the blazing row was actually sparked by Jay-Z, who snapped at Solange when two of her friends tried to use his name to get into the starry after-party at The Standard hotel in Manhattan following the gala last week.
And it was when Solange demanded they leave that Jay-Z said he was heading off to Rihanna's bash without Beyoncé', prompting Solange to hit out at him.

A source said Solange's pals 'wouldn't leave and kept name dropping Jay Z. They were pretending they were guests of his and not hers. Management went to Julius (Beyonce's bodyguard) and said there's a problem.'

Jay-Z soon got wind of it and snapped at Solange, saying 'don't use my name'. This in turn prompted Solange to insist that she wanted to leave the bash.

On the way out, Jay-Z said he'd be heading to Up & Down on West 14th Street, where Rihanna was holding her own post-Met Ball bash, a second source said.

Allegedly, the star said he didn't need extra security because Beyoncé was not joining him.

The source said Solange, who seemed 'drunk and irritated', said: ‘Why can't you go home?' telling Beyonce 'Why does your husband need to go to the club right now?'"

But Jay-Z replied: 'You're one to talk', which sent Solange into a rage.Once inside the elevator, she started punching and kicking her brother-in-law - an attack that was caught on surveillance video and leaked to TMZ.com on Monday.

Ultimately, the rapper decided against going to Rihanna's party and he was seen getting into a separate car as Beyoncé and Solange left together.

Jay-Z and Rihanna are longtime cohorts. While president of Def Jam, he signed the Barbados beauty in 2004 and just days ago she signed to his label Roc Nation.She is also managed by Roc Nation.

Reps for Beyoncé, Jay-Z and Solange did not return requests for comment according to dailymail.

MailOnline told how Jay-Z has reneged on repeated promises to help boost Solange boost music career, according to sources.

And a family friend today revealed the simmering tensions that has led to the family feud, saying: 'He hasn’t kept his promise to help her. Jay keeps telling her to give him some time and he will sit down and write with her and then get her into the studio but he hasn't done it yet.'

The source added: 'Solange's album is coming out soon but there is no buzz about it, which is a bad sign within the industry.

'Solange wants a major career like her sister and she's tired of living in her shadow. She's jealous.

'Jay-Z promised he would help take her to the next level but he never found the time to keep his word.'

UsWeekly has reported that Solange first lost her temper with fashion designer Rachel Roy, a close friend of Kim Kardashian.

The publication claims that Solange 'yelled' at Rachel - who recently attended Kim's baby shower - on the night of the Met Gala after-party.

Beyonce is believed to have got in the middle of an argument between the pair, although it is unclear what it had stemmed from.

It was also reported that Solange was seen arguing with a number of other people at the bash. 

Rachel is considered to be one of Kim Kardashian's closest confidantes and was even invited to Kanye's proposal to Kim last year.