Bastareaud is alleged to have aimed a homophobic slur at Benetton Treviso's Sebastian Negri in a 36-0 victory for Toulon.
The France centre claimed he was reacting to provocation and issued an apology, having appeared to call Negri "f***ing f****t" in the closing stages at Stade Mayol.
Bastareaud could be banned for between six weeks and a year less than a month before the Six Nations starts when he appears before an independent disciplinary committee in London.
Toulon condemned the comments Bastareaud is alleged to have made, but insist they will stand by their captain.
Haskell was sent off for a dangerous late tackle on Harlequins centre Jamie Roberts in the closing stages of Wasps' defeat on Saturday.
Wasps director of rugby Dai Young said he hopes the England flanker's disciplinary record will count in his favour.