Lizzo has been accused for a second time of plagiarism over her hit single Truth Hurts, which recently spent six weeks at No 1 in the US charts.

Songwriter and producer Justin Raisen has posted a video on Instagram comparing Truth Hurts to a song called Healthy that he and others wrote with Lizzo in 2017. The two songs share an opening line – “I just took a DNA test, turns out I’m 100% that bitch” – as well as the same melody, sung in a different key.

“We were never contacted about being credited for the use of the parts of Healthy (melody, lyrics, and chords) that appear in Truth Hurts”, Raisen wrote in a caption to the video. “We’ve tried to sort this out quietly for the last two years, only asking for 5% [songwriting royalties] each, but were shut down every time.”

Raisen said he was making his accusation public owing to “emotional distress … The last thing we want to do is throw any negativity toward Lizzo’s momentum and movement as a cultural figure.”

Lizzo has not responded to the claims. The Guardian was told by Lizzo’s record label that she and they would not be making a comment.

Lizzo’s debut album was released in 2013, but her breakthrough came with her third album, Cuz I Love You, this year. Truth Hurts was released in 2017 but reached the top of the US charts last month, and is her biggest hit to date. She has appeared in the hit movie Hustlers, and has been widely celebrated for her championing of body positivity.

She was first accused of plagiarism in February 2018 by British singer Mina Lioness for the “100% that bitch” lyric, which Lioness originally tweeted in full in February 2017. “Everyone believes those were your words, when in fact they were mine. My creativity, my wit and my comedy,” Lioness tweeted at Lizzo, who replied that she had never seen the tweet and that she was “inspired” by a meme she had seen on Instagram.

In June this year, Lizzo attempted to copyright the phrase “100% that bitch” for use on merchandise. In August, Lioness tweeted: “What I cannot get over is how brazen Lizzo and her team have been in ignoring my whole presence. They’re doing it because they know I have no capital to address her. I’m just the poor Black girl from London that don’t have a dog in the fight.”

Raisen acknowledged Lioness’s tweet in his Instagram post this week, saying: “If [producer] Ricky [Reed] and Lizzo’s team decide to settle this dispute with us, we would like to share some of the proceeds with Mina for her influence on Healthy.”