The Interior Department had no ulterior motive in waiting until last night to issue citations against the companies involved in last year's Deepwater Horizon rig explosion and oil spill, one of the agency's top regulators said today.

Facing GOP criticism of the timing, Bureau of Safety and Environment Enforcement Director Michael Bromwich said his agency held off until last night -- just hours before a hearing on a federal probe into the disaster -- because it needed the time to adequately review the alleged violations.

"I've been pushing since immediately after the issuance of the report to get these out as quickly as possible," Bromwich told reporters after testifying before the House Natural Resources Committee about the Bureau of Ocean Energy Management, Regulation and Enforcement's joint investigation into the disaster with the U.S. Coast Guard.

"It's been frustrating and disappointing to me that it's taken this long, but I've been assured by operational personnel and lawyers that they needed all this time to get it done."

At issue are the 15 citations BSEE issued last night to BP PLC, Halliburton Co. and Transocean Ltd. for their alleged role in last year's oil spill disaster. The four citations each issued to Halliburton and Transocean are the first the Interior Department has ever issued to a drilling contractor.

The Bureau of Safety and Environmental Enforcement accused the companies of failing to keep the well under control, not performing work in a safe manner and discharging pollutants into offshore waters, among others issues.

Committee Chairman Doc Hastings (R-Wash.) questioned the delay in issuing the citations. He said Interior had originally planned to issue the violations three weeks ago, before the committee postponed today's hearing twice.

"I've got serious questions about the timing of these actions," Hastings said.

The BSEE citations could ultimately result in $21.5 million in fines for BP, and millions of dollars more for the other companies involved. But they are not tied to the other fines that the companies could face under the Clean Water Act.

Bromwich said his agency's potential fines would do little to penalize the companies for their alleged roles in the disaster.

"I don't even think it's close," Bromwich said in response to a question from ranking member Ed Markey (D-Mass.). "It needs to be well into the six figures [per day] to be a significant deterrent for the industry."

Republican lawmakers this morning questioned the agency's issuance of the citations to BP's contractors. But Bromwich defended the agency's action.

"That authority has always been there. It has simply been the practice in the past to only go against the operators," he said.

Separately, Bromwich said his agency would not bar BP from participating in its upcoming Gulf of Mexico lease sale in December, the agency's first since the April 2010 rig explosion that killed 11 workers and sparked the nation's worst oil spill.

"We're not going to suspend or debar BP from that sale. We've thought about it a lot, and we don't think it's appropriate in these circumstances," Bromwich said.

Markey said he thought the agency should reconsider.

The discussions cropped up during a hearing on BOEMRE and the Coast Guard's recent probe of the disaster.

The investigative team last month released a 212-page report, which blames much of the 2010 oil spill disaster on poor management decisions by BP and makes a series of regulatory recommendations to improve the safety of offshore drilling.

The probe also faults actions taken by BP's contractors, Halliburton and Transocean.

But representatives of the companies involved in the disaster are staying largely mum about the findings of the report.

"As we have communicated to this committee, while we respect and appreciate the committee's attention to the release of the Joint Investigation Team report, we cannot discuss and comment on the report's findings in any detail because the facts regarding the causes of the accident are the subject of ongoing litigation and investigations regarding the accident," BP America Vice President Raymond Dempsey said.