Johnny Depp and Jeff Beck are suing the professor and folklorist Bruce Jackson over his allegations that the duo’s song Sad Motherfuckin’ Parade on their collaborative album 18 plagiarises a poem written by an incarcerated man.

In August, Jackson accused Depp and Beck of taking lines from the poem which he documented in his 1974 book Get Your Ass in the Water and Swim Like Me. Various lines appear in both works: “I’m raggedy, I know, but I have no stink / God bless the lady that’ll buy me a drink” and “What that funky motherfucker really needs, child, is a bath.”

The poem does not have a definitive author but was recounted to Jackson by an inmate at Missouri State Penitentiary named Slim Wilson. Neither Wilson nor Jackson were named as co-writers of the track.

In the wake of Jackson’s allegations, a spokesperson for the duo said they would review the claims and add additional copyright credits “if appropriate”.

But Rolling Stone reports that the pair have now filed a lawsuit against Jackson for unspecified damages, legal fees and a declaration that they did not commit copyright infringement. Their lawsuit claims that Jackson “owns no copyright in the words” to the poem, only for his own recordings or transcript, which the pair claim they did not infringe.

Jackson told Rolling Stone: “They didn’t write a word of Sad Motherfuckin’ Parade and they are suing the person they stole it from and who caught them doing it. From my point of view, this is like a burglar suing a homeowner because he cut his hand on the kitchen window he broke getting in.”

The suit claims that Jackson sent Depp and Beck letters in August alleging that “nearly every single word” of the song was “copied from Hobo Ben, including the title”. He also allegedly suggested that the “inflection, tonality and rhythm” mirrored the recording he made of Slim Wilson performing the toast in the 1960s, and that Depp and Beck sampled his recording to “construct portions of the vocal track”.

The suit says that Sad Motherfuckin’ Parade is an “original work of authorship and creativity”, but admits that “there may be some elements” of the song that “mirror the words” of Hobo Ben.

Jackson’s lawyers, Rachel and Michael Jackson – also his children – characterised the lawsuit as a “bald attempt to distract the public’s attention away from their repeated attempts to claim authorship for a song that they did not write”.

They accused Depp and Beck of hypocrisy for claiming that it was not possible to have a copyright interest in a toast while also claiming authorship of Sad Motherfuckin’ Parade on the album 18.

Their statement continued: “It is important to understand that Depp and Beck have not denied that the lyrics and nuance of the vocals performed on Sad Motherfuckin’ Parade appear to have been duplicated by Depp and Beck, which they have appropriated and credited to themselves. When this story first broke, Depp and Beck issued a statement to Rolling Stone saying that ‘if appropriate, additional credits will be added to all forms of the album’. Why have they walked away from this promise?”

Depp and Beck’s suit described Jackson’s allegations as an “old-fashioned shakedown”. Jackson’s statement called their claim a “publicity stunt” and clarified that he did not make “formal financial demands” of the pair, but said “any settlement monies would be donated directly to organisations that further his lifelong commitment to preserving African American culture and traditions”.

Depp and Beck’s album 18 received a mostly negative response from critics. In a two-star review, the Guardian’s Michael Hann described it as “a peculiar and hugely uneven record”. In another two-star review, the Independent’s Mark Beaumont said: “It’s tough enough to find any coherent purpose to it, beyond facile Hollywood back-slappery.”