Halsey has hit out at the lack of female artists on the line-up for Firefly Music Festival in Delaware.

The 'Closer' singer is not impressed that American singer/songwriter SZA - whose real name Solána Imani Rowe - is the only woman listed to perform at the music extravaganza, which sees the likes of Eminem, The Killers and Arctic Monkeys on the bill.

Halsey - who previously played the festival in 2015 - wrote on Twitter: ''Damn guys come onnnnnn. Where the women at ... This was one of my favourite festivals I've ever played and it's a shame there's not more females on the bill. With the exception of (the amazing) Sza, the first like 20 acts on the bill are men. It's 2018, do better!!! (sic)''

One of the pop beauty's 8.35 million followers suggested she should complain to the organisers of Firefly, and the 23-year-old star said that there are so many female artists killing it on the music scene, that they have no excuse.

When replying to a fan who has since deleted their tweet, Halsey replied: ''Who am I supposed to 'go off on' haha. Festivals ASK artists to play. Artists don't ASK festivals if they can come. I'm just raising a point! So many dope women in music right now! (sic)''

It seems there are issues across the board with diversity at music events, One Direction's Louis Tomlinson recently hit out at Coachella Valley Music and Arts Festival for not including many bands in their line-up this year.

He wrote on Twitter: ''Just seen the Coachella line up .... Where the f**k are all the bands !? It's a festival !? (sic)''

A number of Louis' fans agreed with him, with some suggesting 1D should be a part of the bill, and while he later insisted it was a ''good line-up'' for the genre, he was still frustrated about the lack of groups.

He added: ''Good line up for that genre but defo not enough bands ! (sic)''

And Ellie Goulding previously bemoaned the lack of women on festival bills.

The 'Still Falling For You' hitmaker wrote: ''Still so proud as a female artist to be headling and playing festivals around the world every single year. Thank you for continually believing in me. It always feels like a triumph to win so many people over who were waiting for a band.

''Need to give myself credit sometimes as I've been doing this nonstop for over seven years. I don't see many females at these festivals. (sic)''