There is evidence to suggest that workers involved in the Deepwater Horizon cleanup operation are not receiving adequate training, according to David Michaels, assistant secretary of labour for the Occupational Safety and Health Administration (OSHA).

Speaking to Risk and Insurance magazine, Mr Michaels expressed particular concern that the Hazardous Waste Operation and Emergency Response (Hazwoper) standards were not being enforced rigorously.

"We have received reports that some are offering this training in significantly less than 40 hours, showing video presentations and offering only limited instruction. This training cannot be shortened to anything less than 40 hours," he told the magazine.

The US Coast Guard has also highlighted the importance of extensive oil and gas training after a further explosion onboard a rig in the Gulf of Mexico.

All 13 crewmembers were rescued from the Mariner Energy rig, which was not actively drilling at the time of the explosion, and the Coast Guard said following emergency operating procedures had been vital to an effective rescue.

Oil and Gas Directory: Training and Development