The reality TV star and heiress - who befriended the I’m Not A Girl, Not Yet A Woman singer in 2006, shortly before her very public breakdown - has spoken out on the Free Britney movement and her conservatorship.
Hilton, 39, told The Sunday Times: "It breaks my heart that people have so much control over her.
“It's not fair to be an adult and be treated like a child. I can't imagine having to live my life like that."
The 38-year-old I’m A Slave 4 U singer was put into her father’s care in 2008.
Jamie Spears stepped down as her conservator last year after 11 years in charge, and her care and finances are now in the hands of her long-term “care manager” Jodi Montgomery.
Britney – who entered the spotlight at the age of 11 on Disney’s The Mickey Mouse Club – suffered from the pressures of fame and work and had a very public breakdown in 2007.
After being put into her father’s care in 2008 she went on to revive her career, appearing as a judge on the American version of The X Factor, performing several hit world tours and starring in a successful Las Vegas residency.
However, she pulled out of a second Las Vegas run due to stress and has not performed since October 2018.
Hilton and Britney have in the past been pictured enjoying nights out together and are believed to be close friends.
Other celebrity endorsers of the Free Britney movement include Miley Cyrus, who encouraged chants of “Free Britney” at her concerts last year.