One of the most controversial tactics used against this summer's Gulf of Mexico oil spill - the construction of large sand islands off the Louisiana coast - managed to stop only a "minuscule" amount of oil, according to a draft report from a presidential commission.

The report, released Thursday, is the latest in a series of findings from the staff of the commission empaneled to investigate the response to the spill.

In this report, staffers found that the "sand berms" - which Louisiana officials had touted as an essential shield against the spill - trapped only about 1,000 barrels of oil out of the approximately 5 million barrels spilled.

For that, the report said, BP paid about $220 million. That, together with $140 million that BP has committed to provide, amounts to one-third of all the money the oil company paid to federal or state governments to help respond to the spill.

Paying "$220 million for a spill response measure that trapped not much more than 1,000 barrels of oil is not a compelling cost-benefit trade-off," the report said.

The report also delved into the decision making of federal officials, who approved about 45 miles of the berms despite objections from scientists that they would do little good and might cause environmental harm.

The report cites an e-mail from Thad W. Allen, the retired Coast Guard admiral who was the federal government's point man on the spill, in which he asked, "What are the chances we could pick a couple of no-brainer projects and call them prototypes to give us some trade space on the larger issue and give that to [Louisiana Gov. Bobby] Jindal this weekend?"

A few days later, the government announced it had approved plans to build one of the six islands that Louisiana wanted as a pilot project.

When President Obama visited Grand Isle, La., on May 28, local officials demanded that more islands be approved. At that meeting, the report says, Obama asked Allen to review the idea .

After that, Allen held a scientific summit on the islands on June 1, where some scientists offered qualified support, the report says. The six-island project was subsequently approved.

BP declined to comment Thursday. Jindal released a statement calling it "partisan revisionist history at taxpayer expense."

The claim "that the berms did not pass the commission's 'cost benefit analysis' is insulting to the thousands of people whose way of life depends on the health of our working coast," Jindal said.

The report says that Allen's decision to green-light the islands was influenced by political pressure, including Obama's request for another review of the idea.

Allen, who has retired from the Coast Guard and gone to work for the Rand Corp., said in a written statement Thursday that the decision was made "based on the outcome" of the scientific meeting he convened.