Andy Paterson, who is behind the new movie Hilary and Jackie, was responding to Mr Lloyd Webber's claims that the film tarnishes the late Ms du Pre's reputation.
The film, which stars Emily Watson as Jacqueline du Pre, is based on the book A Genius in the Family by her brother Piers and sister Hilary, which details multiple sclerosis sufferer Jackie's nervous breakdown and her affair with Hilary's husband.
Mr Lloyd Webber had written in Classic FM Magazine: "My main impression is thatthese revelations are the ultimate act of spite and bitterness."
Mr Lloyd Webber has written "Jackie's Song" - released yesterday - in response to the movie, which he said focused on the negative aspects of the cellist's life, rather than celebrating her music.
However, Mr Paterson, said: "He didn't meet her until she was five years into her illness, so I just don't understand how he can say he knew her better than her own sister.
"Far from tarnishing her memory we'll enhance it and bring it to a new audience. Most of the world has no idea who Jacqueline du Pre is. It's certainly the case that he is exploiting this to promote his CD and himself."
Mr Lloyd Webber said that when the piece was written there were no plans for it to be included on a CD. It was his record company that found space for its release.
"I think they will find I am just the first of a lot of musicians who will speak out for Jacqueline du Pre," he added.Reuse content