5 Seconds of Summer's Luke Hemmings accused of using escorts, cocaine by ex

Boy, oh boy.

Luke Hemmings, the lead singer of Australian boy band 5 Seconds of Summer, is in hot water after his ex-girlfriend went on a fiery Instagram commenting spree.

Luke – who rose to fame with 5S0S after the band opened for One Direction on their 2013 tour – and Arzaylea broke up earlier this year amid rumours that she cheated on him at Coachella with singer Blackbear.

But now, 22-year-old Arzaylea is fighting back.

On Luke's August 19 Instagram post captioned "2fast4u", the model commented, "Yeah you always did finish fast. That [sic] why he was still f---ing me the NIGHT before he went out with another girl? Y'all need to realize none of these guys are perfect. I'm over being the one in trouble lmao."

And she wasn't done.

"We're gunna talk about the escorts. The cocaine. The cheating on ME. The lies," she continued. "Everything that led up to me leaving YOU. IM TIRED OF EVERYONE THINKING THIS IS FOR ATTENTION VECAUSE [sic] DEAD A-- IVE BEEN HOLDIN IN MY PAIN FOR A YEAR. I MADE A MISTAKE BUT HE MADE A MILLION."

She alleged 21-year-old Luke and his 5SOS bandmates' issues went beyond drugs and infidelity: "The racism, judgment, and homophobia that happens in that group. It's disgusting," she wrote. "Y'all don't know the whole story. You will soon! xoxo"

While Luke – who has 6.1-million Instagram followers – has yet to directly comment on the allegations, he posted a photo from 5SOS' recent concert in Osaka, Japan, with the caption, "This is all that matters."

Arzaylea, meanwhile, has shared several topless shots from a beach holiday with friends.