WASHINGTON (Reuters) - A U.S. judge on Wednesday refused a request by environmental groups to reinstate the Obama administration's original moratorium on deepwater drilling set in the wake of the BP Plc oil spill.

Defenders of Wildlife and other groups requested that U.S. District Judge Martin Feldman lift his injunction blocking the moratorium because he had owned stock in several oil and offshore energy companies, arguing that showed he should be disqualified from the case.

Feldman had granted an injunction sought by drilling companies blocking the Obama administration's six-month ban on deepwater drilling below 500 feet.

The judge rejected the groups' request, saying it was "without a basis in law."

Hours before he issued his ruling blocking the drilling moratorium, Feldman sold his holdings in Exxon Mobil, worth less than $15,000, according to his disclosure papers.

The administration has since revised its moratorium to bar drilling using subsea and surface blowout preventers similar to the one used on the BP well, but it too has come under fire for having virtually the same effect as the original suspension.

On Tuesday, one oil drilling company, Ensco Plc, filed a legal challenge to the Obama administration's new moratorium, saying it was arbitrary and the government failed to provide any evidence it would address the risks of deepwater drilling.

That case is also before Judge Feldman.

(Reporting by Jeremy Pelofsky, Editing by Sandra Maler)