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 nearly 5 million barrels spilled.

For that, the report said, BP paid about $220 million. That, together with the $140 million more that BP has committed to pay, amounts to one-third of all the money the oil company has 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.

Louisiana officials pleaded for more, the report says. 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 anew and do it in a week.

After that, Allen held a scientific summit on the islands on June 1. When some scientists offered qualified support, the report says, Allen went out to dinner in New Orleans with BP chief executive Tony Hayward.

Allen "passed on the message to Mr. Hayward, over pasta and Gulf shrimp, that the [entire six-island project] would be approved, and that BP would be asked to pay for it," the report says.

BP declined to comment on the report Thursday.