A lawsuit filed by Caesars Entertainment against the state's top gambling regulator alleges he failed to disclose a potential conflict of interest in a timely manner.

Caesars had been a partner of the Suffolk Downs horse track in a casino bid but withdrew after a background check by commission staff.

The federal lawsuit challenges the "constitutionality, objectivity and fairness" of Caesars' treatment by Massachusetts Gaming Commission Chairman Stephen Crosby.

It says Crosby failed to disclose publicly his friendship and past business relationship with Paul Lohnes, a part-owner of land in Everett on which Wynn Resorts hopes to develop a casino. That proposal could have competed directly with Suffolk Downs for the eastern Massachusetts resort casino license.

A commission spokeswoman says the lawsuit is being reviewed and a statement will be issued later Thursday.