WASHINGTON -- The government said Monday that it is toughening environmental reviews for all new deepwater oil drilling, ending an easy path to oil riches that allowed BP to drill its blown-out well in the Gulf of Mexico with little federal scrutiny.

The step is meant to help redress a history of lax oversight leading up to the April 20 explosion that killed 11 workers and led to the worst oil spill in U.S. history. Some 206 million gallons spilled into the Gulf before BP stopped the leak.

A report by the White House Council on Environmental Quality found that decades-old data provided the basis for exempting BP's drilling permits from any extensive environmental review. Now the Interior Department is banning such "categorical exclusions" for deepwater drilling reviews, at least until it investigates how the exemptions are granted.

"Our decision-making must be fully informed by an understanding of the potential environmental consequences of federal actions permitting offshore oil and gas development," Interior Secretary Ken Salazar said in a statement.

For now, new deepwater drilling is under a temporary moratorium in the Gulf. Once that's lifted, though, Interior's new policy is likely to make it much more time-consuming for oil companies to move forward with new deepwater projects, since environmental assessments will be required.

Such assessments typically include a discussion of the need for the project and a look at its environmental impacts, mitigation and possible alternatives, among other things.