NEW ORLEANS — BP bears most of the blame for the disastrous 2010 spill in the Gulf of Mexico because it cut corners and put profit ahead of safety, a Justice Department attorney said Monday at the opening of a high-stakes trial that could result in the oil company and its partners being forced to pay billions more in damages.

The London-based oil giant acknowledged ‘‘errors in judgment’’ but also cast blame on the owner of the drilling rig and the contractor involved in cementing the well.