Jessie J is being sued for copyright infringement.
California-based singer Will Loomis has filed a suit over "substantially similar compositional elements" between her hit Domino and his song Bright Red Chords, which was released with band Loomis & the Lust in 2009.
The US singer's attorneys claim Jessie and her co-songwriters "wilfully infringed" on copyright and sold "millions of copies of their derivative work", resulting in "significant ill-gotten commercial advantage".
Documents filed to the United States District Court on Monday (25 June) by Will's legal team added:"Will Loomis is a rising star in the music business. Bright Red Chords is among Loomis's most popular songs. It was written in 2008 and rapidly gained popularity."
He is seeking a jury trial and at least $150 000 in damages.
Will has taken to his Facebook page about the matter, posting a video of Jessie performing Domino at Queen Elizabeth's Diamond Jubilee concert earlier this month.
Alongside the clip he wrote: "Check out Jessie J playing our song for the King and Queen (sic)."
He added: "When I wrote this melody in my garage I never imagined it would be sung for the King and Queen of England and I especially never imagined it would be sung by Jessie J (sic)."
Despite Will's claims, England's sole monarch is Queen Elizabeth, and her husband's title is Prince Philip.
Jessie (24) and her representatives have yet to respond to the lawsuit.