In a statement posted to Instagram on June 28, the singer -- who rose to fame alongside Spears first on the "Mickey Mouse Club" and then again as they became internationally beloved pop stars in the early 2000s -- addressed comments made during last week's conservatorship hearing.
Aguilera applauded Spears for condemning the strict legal arrangement she says has wrongly controlled her for the past 13 years.
"These past few days I've been thinking about Britney and everything she is going through," the "Candyman" performer wrote. "It is unacceptable that any woman, or human, wanting to be in control of their own destiny might not be allowed to live life as they wish."
Aguilera then acknowledged what it must feel like for Spears "to be silenced, ignored, bullied or denied support" by those within her inner circle, describing it as "the most depleting, devastating and demeaning thing imaginable."
"The harmful mental and emotional damage this can take on a human spirit is nothing to be taken lightly," she continued. "Every woman must have the right to her own body, her own reproductive system, her own privacy, her own space, her own healing and her own happiness."
Among the claims included in Spears' shocking testimony was the revelation that she's prohibited from removing an IUD, despite wanting to have a baby. Additionally, Spears likened the conservatorship to sex trafficking, going as far to say she's being "enslaved" by her father and co-conservator, Jamie Spears.
While Aguilera admitted she's not privy to every detail of Spears' case, she said she can empathize through their shared experience of fame.
Her statement continued, "The conviction and desperation of this plea for freedom leads me to believe that this person I once knew has been living without compassion or decency from those in control. To a woman who has worked under conditions and pressure unimaginable to most, I promise you she deserves all of the freedom possible to live her happiest life."
"My heart goes out to Britney," Aguilera concluded. "She deserves all the TRUE love and support in the world."
Aguilera joins a growing list of Spears' former collaborators who have publicly supported her request to terminate the conservatorship. Justin Timberlake, who dated Spears from 1999 to 2002, called upon the artist's family to right their alleged wrongs.
Spears' younger sister, Jamie Lynn Spears, broke her silence on the matter earlier Monday. The former "Zoey 101" star denied involvement in Spears' legal turmoil, but said she supports her "100 percent."
Following Spears' testimony, an attorney read a statement in court on Jamie Spears' behalf, which read, "Mr. Spears is sorry to see his daughter suffering and in so much pain. Mr. Spears loves his daughter and misses her very much."