WASHINGTON—Top executives from Exxon Mobil Corp., Chevron Corp. and Royal Dutch Shell PLC sought to distance themselves from rival BP PLC before a congressional panel Tuesday, then took tongue-lashings from lawmakers who accused them of relying on sloppy, "cookie cutter" plans for responding to large-scale oil spills.

The finger-pointing came hours before news that the oil spill was even worse than previously thought.

Scientists...