Britney Spears and Jamie Lynn's social media feud continued on Monday as the pop star seemingly called out her sister for being "so cruel" in an Instagram post.

Spears, 40, re-shared a video of herself working out. The "Toxic" singer wore a bright yellow cropped top and black shorts.

"So I wanted to repost this because d--n !!! Y’all comments are so NICE I might as well serve up another round of this video with my voice on it … I mean why not ??? So as I repost this and get laughed at by most and criticized again for sweating and not looking perfect …," Spears began her caption.

Britney Spears seemingly called out Jamie Lynn on Instagram as the sisters' public feud continues. (Image Group LA/Disney Channel via Getty Images)

She went on to seemingly hit at Jamie Lynn by mentioning the name of her sister's memoir, "The Things I Should Have Said." 

BRITNEY SPEARS CALLS SISTER JAMIE LYNN ‘SCUM’ IN SCATHING ONLINE POST

"I might gain some empathy for myself and say the THE THINGS I SHOULD HAVE SAID …. First, F--K YOU and what’s with the BIG LETTER TALK ??? YOU THINK YOU’RE IMPORTANT !!! AGAIN F--K YOU … And if that’s too offensive, take it with a grain of salt [salt emoji] and sprinkle it over your a--es because you people are so cruel you might need some cleansing !!!! Pssss KEEP SMILING."

Representatives for Spears or Jamie Lynn did not immediately respond to Fox News Digital's requests for comment.

Spears has been criticizing her sister online before and after the release of Jamie Lynn's memoir. Most recently, the pop star called Jamie Lynn "scum" in a scathing Instagram post.

Spears has been criticizing her sister via social media since the news broke that Jamie Lynn was releasing a memoir titled "The Things I Should Have Said." ( Kevin Winter/Getty Images)

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"The nerve of you to sell a book now and talk s--t but your f---ing lying just like you lied about Alexa Nikolas !!!! I wish you would take a lie detector test so all these masses of people see you’re lying through your teeth about me !!!! I wish the almighty, Lord would could come down and show this whole world that you’re lying and making money off of me !!!! You are scum, Jamie Lynn," Spears wrote.

Spears and Jamie Lynn's strained relationship became public in the past year as the "Toxic" singer sought to free herself from her conservatorship.

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Spears' strained relationship with Jamie Lynn became public in the past year as the pop star worked to get rid of her conservatorship. (Paul Drinkwater/NBCU Photo Bank/NBCUniversal via Getty Images via Getty Images)

In Spears' legal fight, the pop star called out her family members both in court and on social media for failing to help free her from the 13-year court order.

Fox News' Melissa Roberto contributed to this report.