Barton tweeted that he would not be returning to QPR in the summer, claiming that the two clubs had an agreement over his future.
"Some strange people think that I'll be playing in the Championship next season?? Good one! QPR might, I won't! #fact," he wrote.
"It's not up to QPR if I stay. Agreement already in place for me to stay here. Can't see QPR wanting me on the wage bill in the Champ."
But Marseille's club president Vincent Labrune was quoted on eurosport.fr as saying: "We would not be against the idea of keeping Joey Barton at OM but he belongs to QPR.
"There is no agreement as suggested by Joey Barton."
Barton's comments also drew a response from QPR chairman Tony Fernandes, who insists the club - not the player - would decide what happens to him this summer.
"For the record QPR players under contract cannot decide where they play. They are under CONTRACT," Fernandes wrote.
In a series of tweets, Barton made a pointed jibe at former manager Mark Hughes and confirmed his desire to stay at Marseille.
He wrote: "My QPR career was over when they decided to listen to the footballing sage, Mark of Hughes...
"I'm loving life in France. Loving Marseille. They love me. All I want to do is give everything for this football club. They backed me when nobody else did, for that I will be eternally grateful. This club is now in my blood, it's impossible to get it out (sic) #ForzaOM.
"I really hope they (QPR) stay up. I have all season. Stay up/go down. Harry stays/goes. I don't want to be part of it. Marseille is my home now."