The 48-year-old rocker his hit out at the 'Black Skinhead' rapper after he stormed the stage at the Grammy Awards on Sunday (10.02.15) to claim Beck should have given his Album of the Year award to Beyoncé, who he insists was more deserving of the prize.
Shirley has now penned an open letter branding Kanye ''petty and ''spoilt'', writing: ''Dear Kanye West, it is YOU who is so busy disrespecting artistry.
''You disrespect your own remarkable talents and more importantly you disrespect the talent, hard work and tenacity of all artists when you go so rudely and savagely after such an accomplished and humble artist like BECK. (sic)''
The Scottish musician goes on to claim that Kanye - who has 19-month-old daughter North with wife Kim Kardashian West - made a ''mockery'' of the music industry when he ranted that it was ''disrespectful to inspiration'' for Beck to be given the accolade.
She continued: ''You make yourself look small and petty and spoilt.
''In attempting to reduce the importance of one great talent over another, you make a mockery of all musicians and music from every genre, including your own. Grow up and stop throwing your toys around. You are making yourself look like a complete t**t.''
The red-haired rocker went on to insist that Beyoncé - whose self-titled 2013 album lost out to Beck's 'Morning Phase' - didn't need him to speak for her.
Shirley added: ''P.S. I am pretty certain Beyoncé doesn't need you fighting any battles on her account.
''Seems like she's got everything covered perfectly well on her own.''
Meanwhile, Beck claims he wasn't upset with Kanye for ruining his big night as he was ''so excited'' to have him join him on stage.
He said: ''I was just so excited he was coming up. He deserves to be on stage as much as anybody. How many great records has he put out in the last five years right? I still love him and think he's genius. I aspire to do what he does.''
Kanye's latest rant comes six years after he interrupted Taylor Swift's speech at the 2009 Video Music Awards to claim Beyoncé's 'Single Ladies' should have won over her 'You Belong To Me' in the Best Female Video category.
His new album Underneath It All is out now.