Katy Perry is in hot water with fans of Britney Spears and they're demanding an apology.

The ‘Roar’ singer angered Spears’ loyal fanbase after she appeared to make joking references to her 2007 mental breakdown, during which she shaved her head bald.

Katy PerryKaty Perry has angered Britney Spears fans

While on the Grammys red carpet last night Perry was asked by presenter Ryan Seacrest about taking a break between albums, to which she replied: “That’s called taking care of your mental health”.

When Seacrest then asked how her time off had gone Perry answered: “Fantastic. And I haven’t shaved my head yet”.

Then in another red carpet interview Perry, who has just dyed her hair platinum blonde, appeared to reference Spears again when she said: “It’s like the last colour in the spectrum that I can do,” in reference to her new hair colour.

“I’ve done all of them and the only thing left to do is shave my head, which I’m really saving for a public breakdown,” she added. “I’m down for that. I’m almost moments away from that, obviously.”

In February 2007 Spears was pictured shaving her head after reportedly leaving a rehab center. Not long after the incident Spears admitted herself to a rehab facility and she has since opened up about her struggles with anxiety during this period.

More: Katy Perry Unveils 'Chained To The Rhythm' With Adorable Hamster Video

On Twitter fans of Spears were quick to come to her defence and blast Perry for making light of her struggles. One fan wrote: “@katyperry U should apologize to @britneyspears. Shame on u Katy. She never shades anyone.”

Another added: "Have always liked Katy Perry very much, have even met her. But after what she said last night, I’ve lost a lot of respect for her…Making a joke about mental health issues isnt OK.”

While a third tweeted: "It's funny that Katy Perry makes fun of Britney shaving her head when that moment is more iconic than Katy's whole career”.

At Sunday night’s awards, Perry also gave the first performance of new track ‘Chained To The Rhythm’. The singer used the performance to criticise President Trump, ending by unveiling a ‘We The People’ backdrop.