A former official with BP's drilling operations in the Gulf of Mexico resigned just months before last year's oil spill because of disagreements with the oil giant over its commitment to safety, according to a class-action federal lawsuit related to the spill.

Documents filed Monday night in Houston claim Kevin Lacy, BP's former senior vice president for drilling operations for the Gulf of Mexico, reached a mutual agreement with the company to resign in December 2009 because he believed the company was not adequately committed to improving safety protocols in offshore drilling operations to the level of its industry peers. The Deepwater Horizon rig explosion occurred on April 20, 2010, killing 11 workers and causing the worst oil spill in U.S. history.

The claims come in an amended version of the lawsuit, originally filed last year, that alleges BP inflated its stock price by hiding information and making false and misleading statements about its safety practices before the Gulf of Mexico oil spill. BP's stock value dropped roughly in half following the oil rig explosion and spill.