Outspoken musician Bon Iver has struck out at the Grammys following Bruno Mars' 2018 wins, stating: "No offence... but you absolutely have to be shitting me."
Mars took several major awards including Album of the Year, Record of the Year, Song of the Year, Best R&B Performance, Best R&B Song and Best R&B Album.
He beat Kiwi songstress Lorde for Album of the Year, as well as Jay-Z, Kendrick Lamar and Childish Gambino.
Grammy-winning alumni Bon Iver, real name Justin Vernon, took to Twitter to express his anger at the result.
"Looks like Grammys are still something serious musicians should not take seriously!" he wrote.
"Absolutely NO offence to Mr Mars, but you absolutely have to be shitting me. While some awesome musicians do win, what is WINNING?
"I'd say move on from this shit show. Felt like a Democratic Party Party, not R'n'Roll."
Vernon also slammed Grammys producer Ken Ehrlich over the decision not to offer Lorde a solo performance - the only Best Album nominee to be snubbed.
"I don't know if it was a mistake. These shows are a matter of choices," said Ehrlich.
"Sometimes people get left out that shouldn't, but on the other hand, we did the best we can to make sure that it's a representative and balanced show."
Vernon wrote that Ken Elrich was a "dick producer" and he was "siding with Lorde on this one".