WASHINGTON — Shortly before 10 p.m. on April 20, 2010, an explosion ripped through the Deepwater Horizon drilling rig in the Gulf of Mexico, unleashing the worst offshore oil spill in United States history and triggering what were supposed to be systemic changes to ensure such a disaster could never happen again.

Now, a decade later, all seven members of the bipartisan national commission set up to find the roots of the disaster and prevent a repeat said many of their recommendations were never taken seriously. As drilling moves farther offshore and deeper underwater, they said, another spill of equally disastrous proportions is possible.

All seven members, in fact, agreed that the United States was only marginally better prepared than it was the night eleven people died in the fiery blowout that released more than 3 million barrels of oil into the waters off the coast of Louisiana.

“No, I don’t think we’re prepared for another spill of that magnitude,” said William K. Reilly, the commission’s Republican co-chairman, who served as administrator of the Environmental Protection Agency under the first President George Bush.