WASHINGTON  A federal judge in New Orleans on Thursday ordered the Obama administration to move quickly on permits for new deepwater oil wells in the Gulf of Mexico, saying that the government could no longer justify long delays in allowing new projects to go forward.

Judge Martin Feldman, of the United States District Court for the Eastern District of Louisiana, said that the Interior Department was required to act on drilling applications “within a reasonable time.”

“Not acting at all is not a lawful option,” Judge Feldman wrote, adding that the delays are “increasingly inexcusable” and were causing drilling companies to relocate their rigs to foreign waters.

The interior secretary, Ken Salazar, imposed a six-month moratorium on deepwater drilling in the gulf immediately after the Deepwater Horizon explosion in April, which killed 11 workers and spilled nearly five million barrels of oil into the ocean. Judge Feldman declared the drilling ban illegal in June, but Mr. Salazar modified it slightly, and it remained in place until the department lifted it in October.